Tutorial: verifica dei dati utilizzando un SDK AWS - Database Amazon Quantum Ledger (Amazon QLDB)
PrerequisitiPassaggio 1: richiedi un riassuntoPassaggio 2: interrogare la revisione del documentoFase 3: Richiedere una bozza della revisioneFase 4: Ricalcola il digest dalla revisioneFase 5: Richiedere una bozza per il blocco journalFase 6: Ricalcola il digest dal bloccoEsegui l'esempio completo di codice

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Tutorial: verifica dei dati utilizzando un SDK AWS

In questo tutorial, verifichi un hash di revisione del documento e un hash del blocco journal in un registro Amazon QLDB utilizzando l'API QLDB tramite un SDK. AWS È inoltre possibile utilizzare il driver QLDB per interrogare la revisione del documento.

Si consideri un esempio in cui si dispone di una revisione del documento che contiene i dati di un veicolo con un numero di identificazione del veicolo (VIN) di. KM8SRDHF6EU074761 La revisione del documento si trova in una VehicleRegistration tabella che si trova in un registro denominato. vehicle-registration Supponiamo di voler verificare l'integrità sia della revisione del documento per questo veicolo sia del blocco del giornale che contiene la revisione.

Nota

Per un post dettagliato AWS sul blog che illustra il valore della verifica crittografica nel contesto di un caso d'uso realistico, consulta Verifica crittografica nel mondo reale con Amazon QLDB.

Prerequisiti

Prima di iniziare, assicurati di fare quanto segue:

  1. Configura il driver QLDB per una lingua a tua scelta completando i rispettivi prerequisiti sotto. Nozioni base sul driver Amazon QLDB Ciò include la registrazione AWS, la concessione dell'accesso programmatico per lo sviluppo e la configurazione dell'ambiente di sviluppo.

  2. Segui i passaggi da 1 Nozioni di base sulla console Amazon QLDB a 2 per creare un registro denominato vehicle-registration e caricarlo con dati di esempio predefiniti.

Successivamente, esamina i passaggi seguenti per scoprire come funziona la verifica, quindi esegui l'esempio di codice completo dall'inizio alla fine.

Passaggio 1: richiedi un riassunto

Prima di poter verificare i dati, devi prima richiedere un riepilogo dal registro vehicle-registration per utilizzarlo in un secondo momento.

Java
// Get a digest
GetDigestRequest digestRequest = new GetDigestRequest().withName(ledgerName);
GetDigestResult digestResult = client.getDigest(digestRequest);

java.nio.ByteBuffer digest = digestResult.getDigest();

// expectedDigest is the buffer we will use later to compare against our calculated digest
byte[] expectedDigest = new byte[digest.remaining()];
digest.get(expectedDigest);
.NET
// Get a digest
GetDigestRequest getDigestRequest = new GetDigestRequest
{
    Name = ledgerName
};
GetDigestResponse getDigestResponse = client.GetDigestAsync(getDigestRequest).Result;

// expectedDigest is the buffer we will use later to compare against our calculated digest
MemoryStream digest = getDigestResponse.Digest;
byte[] expectedDigest = digest.ToArray();
Go
// Get a digest
currentLedgerName := ledgerName
input := qldb.GetDigestInput{Name: &currentLedgerName}
digestOutput, err := client.GetDigest(&input)
if err != nil {
    panic(err)
}

// expectedDigest is the buffer we will later use to compare against our calculated digest
expectedDigest := digestOutput.Digest
Node.js
// Get a digest
const getDigestRequest: GetDigestRequest = {
    Name: ledgerName
};
const getDigestResponse: GetDigestResponse = await qldbClient.getDigest(getDigestRequest).promise();

// expectedDigest is the buffer we will later use to compare against our calculated digest
const expectedDigest: Uint8Array = <Uint8Array>getDigestResponse.Digest;
Python
# Get a digest
get_digest_response = qldb_client.get_digest(Name=ledger_name)

# expected_digest is the buffer we will later use to compare against our calculated digest
expected_digest = get_digest_response.get('Digest')
digest_tip_address = get_digest_response.get('DigestTipAddress')

Passaggio 2: interrogare la revisione del documento

Usa il driver QLDB per interrogare gli indirizzi di blocco, gli hash e gli ID dei documenti associati al VIN. KM8SRDHF6EU074761

Java
// Retrieve info for the given vin's document revisions
Result result = driver.execute(txn -> {
    final String query = String.format("SELECT blockAddress, hash, metadata.id FROM _ql_committed_%s WHERE data.VIN = '%s'", tableName, vin);
    return txn.execute(query);
});
.NET
// Retrieve info for the given vin's document revisions
var result = driver.Execute(txn => {
    string query = $"SELECT blockAddress, hash, metadata.id FROM _ql_committed_{tableName} WHERE data.VIN = '{vin}'";
    return txn.Execute(query);
});
Go
// Retrieve info for the given vin's document revisions
result, err := driver.Execute(context.Background(), func(txn qldbdriver.Transaction) (interface{}, error) {
    statement := fmt.Sprintf(
            "SELECT blockAddress, hash, metadata.id FROM _ql_committed_%s WHERE data.VIN = '%s'",
            tableName,
            vin)
    result, err := txn.Execute(statement)
    if err != nil {
        return nil, err
    }

    results := make([]map[string]interface{}, 0)

    // Convert the result set into a map
    for result.Next(txn) {
        var doc map[string]interface{}
        err := ion.Unmarshal(result.GetCurrentData(), &doc)
        if err != nil {
            return nil, err
        }
        results = append(results, doc)
    }
    return results, nil
})
if err != nil {
    panic(err)
}
resultSlice := result.([]map[string]interface{})
Node.js
const result: dom.Value[] = await driver.executeLambda(async (txn: TransactionExecutor): Promise<dom.Value[]> => {
    const query: string = `SELECT blockAddress, hash, metadata.id FROM _ql_committed_${tableName} WHERE data.VIN = '${vin}'`;
    const queryResult: Result = await txn.execute(query);
    return queryResult.getResultList();
});
Python
def query_doc_revision(txn):
    query = "SELECT blockAddress, hash, metadata.id FROM _ql_committed_{} WHERE data.VIN = '{}'".format(table_name, vin)
    return txn.execute_statement(query)

# Retrieve info for the given vin's document revisions
result = qldb_driver.execute_lambda(query_doc_revision)

Fase 3: Richiedere una bozza della revisione

Esegui un'iterazione dei risultati della query e utilizza ogni indirizzo di blocco e ID del documento insieme al nome del libro mastro per inviare una richiesta. GetRevision Per ottenere una bozza della revisione, devi anche fornire l'indirizzo del suggerimento contenuto nel digest salvato in precedenza. Questa operazione API restituisce un oggetto che include la revisione del documento e la bozza della revisione.

Per informazioni sulla struttura di revisione e sul relativo contenuto, vedere. Interrogazione dei metadati dei documenti

Java
for (IonValue ionValue : result) {
    IonStruct ionStruct = (IonStruct)ionValue;

    // Get the requested fields
    IonValue blockAddress = ionStruct.get("blockAddress");
    IonBlob hash = (IonBlob)ionStruct.get("hash");
    String metadataId = ((IonString)ionStruct.get("id")).stringValue();

    System.out.printf("Verifying document revision for id '%s'%n", metadataId);

    String blockAddressText = blockAddress.toString();

    // Submit a request for the revision
    GetRevisionRequest revisionRequest = new GetRevisionRequest()
            .withName(ledgerName)
            .withBlockAddress(new ValueHolder().withIonText(blockAddressText))
            .withDocumentId(metadataId)
            .withDigestTipAddress(digestResult.getDigestTipAddress());

    // Get a result back
    GetRevisionResult revisionResult = client.getRevision(revisionRequest);

    ...
}
.NET
foreach (IIonValue ionValue in result)
{
    IIonStruct ionStruct = ionValue;

    // Get the requested fields
    IIonValue blockAddress = ionStruct.GetField("blockAddress");
    IIonBlob hash = ionStruct.GetField("hash");
    String metadataId = ionStruct.GetField("id").StringValue;

    Console.WriteLine($"Verifying document revision for id '{metadataId}'");

    // Use an Ion Reader to convert block address to text
    IIonReader reader = IonReaderBuilder.Build(blockAddress);
    StringWriter sw = new StringWriter();
    IIonWriter textWriter = IonTextWriterBuilder.Build(sw);
    textWriter.WriteValues(reader);
    string blockAddressText = sw.ToString();

    // Submit a request for the revision
    GetRevisionRequest revisionRequest = new GetRevisionRequest
    {
        Name = ledgerName,
        BlockAddress = new ValueHolder
        {
            IonText = blockAddressText
        },
        DocumentId = metadataId,
        DigestTipAddress = getDigestResponse.DigestTipAddress
    };
    
    // Get a response back
    GetRevisionResponse revisionResponse = client.GetRevisionAsync(revisionRequest).Result;

    ...
}
Go
for _, value := range resultSlice {
    // Get the requested fields
    ionBlockAddress, err := ion.MarshalText(value["blockAddress"])
    if err != nil {
        panic(err)
    }
    blockAddress := string(ionBlockAddress)
    metadataId := value["id"].(string)
    documentHash := value["hash"].([]byte)

    fmt.Printf("Verifying document revision for id '%s'\n", metadataId)

    // Submit a request for the revision
    revisionInput := qldb.GetRevisionInput{
        BlockAddress:     &qldb.ValueHolder{IonText: &blockAddress},
        DigestTipAddress: digestOutput.DigestTipAddress,
        DocumentId:       &metadataId,
        Name:             &currentLedgerName,
    }

    // Get a result back
    revisionOutput, err := client.GetRevision(&revisionInput)
    if err != nil {
        panic(err)
    }

    ...
}
Node.js
for (let value of result) {
    // Get the requested fields
    const blockAddress: dom.Value = value.get("blockAddress");
    const hash: dom.Value = value.get("hash");
    const metadataId: string = value.get("id").stringValue();

    console.log(`Verifying document revision for id '${metadataId}'`);

    // Submit a request for the revision
    const revisionRequest: GetRevisionRequest = {
        Name: ledgerName,
        BlockAddress: {
            IonText: dumpText(blockAddress)
        },
        DocumentId: metadataId,
        DigestTipAddress: getDigestResponse.DigestTipAddress
    };

    // Get a response back
    const revisionResponse: GetRevisionResponse = await qldbClient.getRevision(revisionRequest).promise();

    ...
}
Python
for value in result:
    # Get the requested fields
    block_address = value['blockAddress']
    document_hash = value['hash']
    metadata_id = value['id']

    print("Verifying document revision for id '{}'".format(metadata_id))

    # Submit a request for the revision and get a result back
    proof_response = qldb_client.get_revision(Name=ledger_name,
                                              BlockAddress=block_address_to_dictionary(block_address),
                                              DocumentId=metadata_id,
                                              DigestTipAddress=digest_tip_address)

Recuperate quindi la bozza della revisione richiesta.

L'API QLDB restituisce la dimostrazione come rappresentazione in formato stringa dell'elenco ordinato degli hash dei nodi. Per convertire questa stringa in un elenco della rappresentazione binaria degli hash del nodo, puoi utilizzare un lettore di ioni dalla libreria Amazon Ion. Per ulteriori informazioni sull'uso della libreria Ion, consulta Amazon Ion Cookbook.

Java

In questo esempio, si utilizza IonReader per eseguire la conversione binaria.

String proofText = revisionResult.getProof().getIonText();

// Take the proof and convert it to a list of byte arrays
List<byte[]> internalHashes = new ArrayList<>();
IonReader reader = SYSTEM.newReader(proofText);
reader.next();
reader.stepIn();
while (reader.next() != null) {
    internalHashes.add(reader.newBytes());
}
.NET

In questo esempio, si utilizza IonLoader per caricare la bozza in un datagramma ionico.

string proofText = revisionResponse.Proof.IonText;
IIonDatagram proofValue = IonLoader.Default.Load(proofText);
Go

In questo esempio, si utilizza un lettore Ion per convertire la dimostrazione in binario e per scorrere l'elenco degli hash dei nodi della bozza.

proofText := revisionOutput.Proof.IonText

// Use ion.Reader to iterate over the proof's node hashes
reader := ion.NewReaderString(*proofText)
// Enter the struct containing node hashes
reader.Next()
if err := reader.StepIn(); err != nil {
    panic(err)
}
Node.js

In questo esempio, si utilizza la load funzione per eseguire la conversione binaria.

let proofValue: dom.Value = load(revisionResponse.Proof.IonText);
Python

In questo esempio, si utilizza la loads funzione per eseguire la conversione binaria.

proof_text = proof_response.get('Proof').get('IonText')
proof_hashes = loads(proof_text)

Fase 4: Ricalcola il digest dalla revisione

Usa l'elenco di hash della bozza per ricalcolare il digest, iniziando dall'hash della revisione. Finché il digest salvato in precedenza è noto e affidabile al di fuori di QLDB, l'integrità della revisione del documento è dimostrata se l'hash del digest ricalcolato corrisponde all'hash del digest salvato.

Java
// Calculate digest
byte[] calculatedDigest = internalHashes.stream().reduce(hash.getBytes(), BlockHashVerification::dot);

boolean verified = Arrays.equals(expectedDigest, calculatedDigest);

if (verified) {
    System.out.printf("Successfully verified document revision for id '%s'!%n", metadataId);
} else {
    System.out.printf("Document revision for id '%s' verification failed!%n", metadataId);
    return;
}
.NET
byte[] documentHash = hash.Bytes().ToArray();
foreach (IIonValue proofHash in proofValue.GetElementAt(0))
{
    // Calculate the digest
    documentHash = Dot(documentHash, proofHash.Bytes().ToArray());
}

bool verified = expectedDigest.SequenceEqual(documentHash);

if (verified)
{
    Console.WriteLine($"Successfully verified document revision for id '{metadataId}'!");
}
else
{
    Console.WriteLine($"Document revision for id '{metadataId}' verification failed!");
    return;
}
Go
// Going through nodes and calculate digest
for reader.Next() {
    val, _ := reader.ByteValue()
    documentHash, err = dot(documentHash, val)
}

// Compare documentHash with the expected digest
verified := reflect.DeepEqual(documentHash, expectedDigest)

if verified {
    fmt.Printf("Successfully verified document revision for id '%s'!\n", metadataId)
} else {
    fmt.Printf("Document revision for id '%s' verification failed!\n", metadataId)
    return
}
Node.js
let documentHash: Uint8Array = hash.uInt8ArrayValue();
proofValue.elements().forEach((proofHash: dom.Value) => {
    // Calculate the digest
    documentHash = dot(documentHash, proofHash.uInt8ArrayValue());
});

let verified: boolean = isEqual(expectedDigest, documentHash);

if (verified) {
    console.log(`Successfully verified document revision for id '${metadataId}'!`);
} else {
    console.log(`Document revision for id '${metadataId}' verification failed!`);
    return;
}
Python
# Calculate digest
calculated_digest = reduce(dot, proof_hashes, document_hash)

verified = calculated_digest == expected_digest
if verified:
    print("Successfully verified document revision for id '{}'!".format(metadata_id))
else:
    print("Document revision for id '{}' verification failed!".format(metadata_id))

Fase 5: Richiedere una bozza per il blocco journal

Successivamente, si verifica il blocco del diario che contiene la revisione del documento.

Utilizza l'indirizzo di blocco e l'indirizzo tip del digest che hai salvato nel passaggio 1 per inviare una GetBlock richiesta. Analogamente alla GetRevision richiesta nella Fase 2, devi fornire nuovamente l'indirizzo del suggerimento contenuto nel digest salvato per ottenere una prova dell'esistenza del blocco. Questa operazione API restituisce un oggetto che include il blocco e la bozza del blocco.

Per informazioni sulla struttura del blocco journal e sul relativo contenuto, vedereContenuto del diario in Amazon QLDB.

Java
// Submit a request for the block
GetBlockRequest getBlockRequest = new GetBlockRequest()
        .withName(ledgerName)
        .withBlockAddress(new ValueHolder().withIonText(blockAddressText))
        .withDigestTipAddress(digestResult.getDigestTipAddress());

// Get a result back
GetBlockResult getBlockResult = client.getBlock(getBlockRequest);
.NET
// Submit a request for the block
GetBlockRequest getBlockRequest = new GetBlockRequest
{
    Name = ledgerName,
    BlockAddress = new ValueHolder
    {
        IonText = blockAddressText
    },
    DigestTipAddress = getDigestResponse.DigestTipAddress
};

// Get a response back
GetBlockResponse getBlockResponse = client.GetBlockAsync(getBlockRequest).Result;
Go
// Submit a request for the block
blockInput := qldb.GetBlockInput{
    Name:             &currentLedgerName,
    BlockAddress:     &qldb.ValueHolder{IonText: &blockAddress},
    DigestTipAddress: digestOutput.DigestTipAddress,
}

// Get a result back
blockOutput, err := client.GetBlock(&blockInput)
if err != nil {
    panic(err)
}
Node.js
// Submit a request for the block
const getBlockRequest: GetBlockRequest = {
    Name: ledgerName,
    BlockAddress: {
        IonText: dumpText(blockAddress)
    },
    DigestTipAddress: getDigestResponse.DigestTipAddress
};

// Get a response back
const getBlockResponse: GetBlockResponse = await qldbClient.getBlock(getBlockRequest).promise();
Python
def block_address_to_dictionary(ion_dict):
"""
Convert a block address from IonPyDict into a dictionary.
Shape of the dictionary must be: {'IonText': "{strandId: <"strandId">, sequenceNo: <sequenceNo>}"}

:type ion_dict: :py:class:`amazon.ion.simple_types.IonPyDict`/str
:param ion_dict: The block address value to convert.

:rtype: dict
:return: The converted dict.
"""
block_address = {'IonText': {}}
if not isinstance(ion_dict, str):
    py_dict = '{{strandId: "{}", sequenceNo:{}}}'.format(ion_dict['strandId'], ion_dict['sequenceNo'])
    ion_dict = py_dict
block_address['IonText'] = ion_dict
return block_address

# Submit a request for the block and get a result back
block_response = qldb_client.get_block(Name=ledger_name, BlockAddress=block_address_to_dictionary(block_address),
                                       DigestTipAddress=digest_tip_address)

Quindi, recupera l'hash del blocco e la dimostrazione dal risultato.

Java

In questo esempio, si utilizza IonLoader per caricare l'oggetto blocco in un IonDatagram contenitore.

String blockText = getBlockResult.getBlock().getIonText();

IonDatagram datagram = SYSTEM.getLoader().load(blockText);
ionStruct = (IonStruct)datagram.get(0);

final byte[] blockHash = ((IonBlob)ionStruct.get("blockHash")).getBytes();

Utilizzate anche IonLoader per caricare la bozza in un fileIonDatagram.

proofText = getBlockResult.getProof().getIonText();

// Take the proof and create a list of hash binary data
datagram = SYSTEM.getLoader().load(proofText);
ListIterator<IonValue> listIter = ((IonList)datagram.iterator().next()).listIterator();

internalHashes.clear();
while (listIter.hasNext()) {
    internalHashes.add(((IonBlob)listIter.next()).getBytes());
}
.NET

In questo esempio, si utilizza IonLoader per caricare il blocco e la bozza in un datagramma ionico per ciascuno.

string blockText = getBlockResponse.Block.IonText;
IIonDatagram blockValue = IonLoader.Default.Load(blockText);

// blockValue is a IonDatagram, and the first value is an IonStruct containing the blockHash
byte[] blockHash = blockValue.GetElementAt(0).GetField("blockHash").Bytes().ToArray();

proofText = getBlockResponse.Proof.IonText;
proofValue = IonLoader.Default.Load(proofText);
Go

In questo esempio, utilizzate un lettore Ion per convertire la bozza in binario e per scorrere l'elenco degli hash dei nodi della bozza.

proofText = blockOutput.Proof.IonText

block := new(map[string]interface{})
err = ion.UnmarshalString(*blockOutput.Block.IonText, block)
if err != nil {
    panic(err)
}

blockHash := (*block)["blockHash"].([]byte)

// Use ion.Reader to iterate over the proof's node hashes
reader = ion.NewReaderString(*proofText)
// Enter the struct containing node hashes
reader.Next()
if err := reader.StepIn(); err != nil {
    panic(err)
}
Node.js

In questo esempio, si utilizza la load funzione per convertire il blocco e la dimostrazione in binario.

const blockValue: dom.Value = load(getBlockResponse.Block.IonText)
let blockHash: Uint8Array = blockValue.get("blockHash").uInt8ArrayValue();

proofValue = load(getBlockResponse.Proof.IonText);
Python

In questo esempio, si utilizza la loads funzione per convertire il blocco e la dimostrazione in binario.

block_text = block_response.get('Block').get('IonText')
block = loads(block_text)

block_hash = block.get('blockHash')

proof_text = block_response.get('Proof').get('IonText')
proof_hashes = loads(proof_text)

Fase 6: Ricalcola il digest dal blocco

Usa l'elenco di hash del proof per ricalcolare il digest, iniziando dall'hash del blocco. Finché il digest salvato in precedenza è noto e affidabile al di fuori di QLDB, l'integrità del blocco viene dimostrata se l'hash del digest ricalcolato corrisponde all'hash del digest salvato.

Java
// Calculate digest
calculatedDigest = internalHashes.stream().reduce(blockHash, BlockHashVerification::dot);

verified = Arrays.equals(expectedDigest, calculatedDigest);

if (verified) {
    System.out.printf("Block address '%s' successfully verified!%n", blockAddressText);
} else {
    System.out.printf("Block address '%s' verification failed!%n", blockAddressText);
}
.NET
foreach (IIonValue proofHash in proofValue.GetElementAt(0))
{
    // Calculate the digest
    blockHash = Dot(blockHash, proofHash.Bytes().ToArray());
}

verified = expectedDigest.SequenceEqual(blockHash);

if (verified)
{
    Console.WriteLine($"Block address '{blockAddressText}' successfully verified!");
}
else
{
    Console.WriteLine($"Block address '{blockAddressText}' verification failed!");
}
Go
// Going through nodes and calculate digest
for reader.Next() {
    val, err := reader.ByteValue()
    if err != nil {
        panic(err)
    }
    blockHash, err = dot(blockHash, val)
}

// Compare blockHash with the expected digest
verified = reflect.DeepEqual(blockHash, expectedDigest)

if verified {
    fmt.Printf("Block address '%s' successfully verified!\n", blockAddress)
} else {
    fmt.Printf("Block address '%s' verification failed!\n", blockAddress)
    return
}
Node.js
proofValue.elements().forEach((proofHash: dom.Value) => {
    // Calculate the digest
    blockHash = dot(blockHash, proofHash.uInt8ArrayValue());
});

verified = isEqual(expectedDigest, blockHash);

if (verified) {
    console.log(`Block address '${dumpText(blockAddress)}' successfully verified!`);
} else {
    console.log(`Block address '${dumpText(blockAddress)}' verification failed!`);
}
Python
# Calculate digest
calculated_digest = reduce(dot, proof_hashes, block_hash)

verified = calculated_digest == expected_digest
if verified:
    print("Block address '{}' successfully verified!".format(dumps(block_address,
                                                                   binary=False,
                                                                   omit_version_marker=True)))
else:
    print("Block address '{}' verification failed!".format(block_address))

Gli esempi di codice precedenti utilizzano la seguente funzione per ricalcolare il digest. dot Questa funzione accetta l'input di due hash, li ordina, li concatena e quindi restituisce l'hash dell'array concatenato.

Java
/**
 * Takes two hashes, sorts them, concatenates them, and then returns the
 * hash of the concatenated array.
 *
 * @param h1
 *              Byte array containing one of the hashes to compare.
 * @param h2
 *              Byte array containing one of the hashes to compare.
 * @return the concatenated array of hashes.
 */
public static byte[] dot(final byte[] h1, final byte[] h2) {
    if (h1.length != HASH_LENGTH || h2.length != HASH_LENGTH) {
        throw new IllegalArgumentException("Invalid hash.");
    }

    int byteEqual = 0;
    for (int i = h1.length - 1; i >= 0; i--) {
        byteEqual = Byte.compare(h1[i], h2[i]);
        if (byteEqual != 0) {
            break;
        }
    }

    byte[] concatenated = new byte[h1.length + h2.length];
    if (byteEqual < 0) {
        System.arraycopy(h1, 0, concatenated, 0, h1.length);
        System.arraycopy(h2, 0, concatenated, h1.length, h2.length);
    } else {
        System.arraycopy(h2, 0, concatenated, 0, h2.length);
        System.arraycopy(h1, 0, concatenated, h2.length, h1.length);
    }

    MessageDigest messageDigest;
    try {
        messageDigest = MessageDigest.getInstance("SHA-256");
    } catch (NoSuchAlgorithmException e) {
        throw new IllegalStateException("SHA-256 message digest is unavailable", e);
    }

    messageDigest.update(concatenated);
    return messageDigest.digest();
}
.NET
/// <summary>
/// Takes two hashes, sorts them, concatenates them, and then returns the
/// hash of the concatenated array.
/// </summary>
/// <param name="h1">Byte array containing one of the hashes to compare.</param>
/// <param name="h2">Byte array containing one of the hashes to compare.</param>
/// <returns>The concatenated array of hashes.</returns>
private static byte[] Dot(byte[] h1, byte[] h2)
{
    if (h1.Length == 0)
    {
        return h2;
    }

    if (h2.Length == 0)
    {
        return h1;
    }

    HashAlgorithm hashAlgorithm = HashAlgorithm.Create("SHA256");
    HashComparer comparer = new HashComparer();
    if (comparer.Compare(h1, h2) < 0)
    {
        return hashAlgorithm.ComputeHash(h1.Concat(h2).ToArray());
    }
    else
    {
        return hashAlgorithm.ComputeHash(h2.Concat(h1).ToArray());
    }
}

private class HashComparer : IComparer<byte[]>
{
    private static readonly int HASH_LENGTH = 32;

    public int Compare(byte[] h1, byte[] h2)
    {
        if (h1.Length != HASH_LENGTH || h2.Length != HASH_LENGTH)
        {
            throw new ArgumentException("Invalid hash");
        }

        for (var i = h1.Length - 1; i >= 0; i--)
        {
            var byteEqual = (sbyte)h1[i] - (sbyte)h2[i];
            if (byteEqual != 0)
            {
                return byteEqual;
            }
        }

        return 0;
    }
}
Go
// Takes two hashes, sorts them, concatenates them, and then returns the hash of the concatenated array.
func dot(h1, h2 []byte) ([]byte, error) {
    compare, err := hashComparator(h1, h2)
    if err != nil {
        return nil, err
    }

    var concatenated []byte
    if compare < 0 {
        concatenated = append(h1, h2...)
    } else {
        concatenated = append(h2, h1...)
    }

    newHash := sha256.Sum256(concatenated)
    return newHash[:], nil
}

func hashComparator(h1 []byte, h2 []byte) (int16, error) {
    if len(h1) != hashLength || len(h2) != hashLength {
        return 0, errors.New("invalid hash")
    }
    for i := range h1 {
        // Reverse index for little endianness
        index := hashLength - 1 - i

        // Handle byte being unsigned and overflow
        h1Int := int16(h1[index])
        h2Int := int16(h2[index])
        if h1Int > 127 {
            h1Int = 0 - (256 - h1Int)
        }
        if h2Int > 127 {
            h2Int = 0 - (256 - h2Int)
        }

        difference := h1Int - h2Int
        if difference != 0 {
            return difference, nil
        }
    }
    return 0, nil
}
Node.js
/**
 * Takes two hashes, sorts them, concatenates them, and calculates a digest based on the concatenated hash.
 * @param h1 Byte array containing one of the hashes to compare.
 * @param h2 Byte array containing one of the hashes to compare.
 * @returns The digest calculated from the concatenated hash values.
 */
function dot(h1: Uint8Array, h2: Uint8Array): Uint8Array {
    if (h1.length === 0) {
        return h2;
    }
    if (h2.length === 0) {
        return h1;
    }

    const newHashLib = createHash("sha256");

    let concatenated: Uint8Array;
    if (hashComparator(h1, h2) < 0) {
        concatenated = concatenate(h1, h2);
    } else {
        concatenated = concatenate(h2, h1);
    }
    newHashLib.update(concatenated);
    return newHashLib.digest();
}

/**
 * Compares two hashes by their **signed** byte values in little-endian order.
 * @param hash1 The hash value to compare.
 * @param hash2 The hash value to compare.
 * @returns Zero if the hash values are equal, otherwise return the difference of the first pair of non-matching
 *          bytes.
 * @throws RangeError When the hash is not the correct hash size.
 */
function hashComparator(hash1: Uint8Array, hash2: Uint8Array): number {
    if (hash1.length !== HASH_SIZE || hash2.length !== HASH_SIZE) {
        throw new RangeError("Invalid hash.");
    }
    for (let i = hash1.length-1; i >= 0; i--) {
        const difference: number = (hash1[i]<<24 >>24) - (hash2[i]<<24 >>24);
        if (difference !== 0) {
            return difference;
        }
    }
    return 0;
}

/**
 * Helper method that concatenates two Uint8Array.
 * @param arrays List of arrays to concatenate, in the order provided.
 * @returns The concatenated array.
 */
function concatenate(...arrays: Uint8Array[]): Uint8Array {
    let totalLength = 0;
    for (const arr of arrays) {
        totalLength += arr.length;
    }
    const result = new Uint8Array(totalLength);
    let offset = 0;
    for (const arr of arrays) {
        result.set(arr, offset);
        offset += arr.length;
    }
    return result;
}

/**
 * Helper method that checks for equality between two Uint8Array.
 * @param expected Byte array containing one of the hashes to compare.
 * @param actual Byte array containing one of the hashes to compare.
 * @returns Boolean indicating equality between the two Uint8Array.
 */
function isEqual(expected: Uint8Array, actual: Uint8Array): boolean {
    if (expected === actual) return true;
    if (expected == null || actual == null) return false;
    if (expected.length !== actual.length) return false;

    for (let i = 0; i < expected.length; i++) {
        if (expected[i] !== actual[i]) {
            return false;
        }
    }
    return true;
}
Python
def dot(hash1, hash2):
    """
    Takes two hashes, sorts them, concatenates them, and then returns the
    hash of the concatenated array.

    :type hash1: bytes
    :param hash1: The hash value to compare.

    :type hash2: bytes
    :param hash2: The hash value to compare.

    :rtype: bytes
    :return: The new hash value generated from concatenated hash values.
    """
    if len(hash1) != hash_length or len(hash2) != hash_length:
        raise ValueError('Illegal hash.')

    hash_array1 = array('b', hash1)
    hash_array2 = array('b', hash2)

    difference = 0
    for i in range(len(hash_array1) - 1, -1, -1):
        difference = hash_array1[i] - hash_array2[i]
        if difference != 0:
            break

    if difference < 0:
        concatenated = hash1 + hash2
    else:
        concatenated = hash2 + hash1

    new_hash_lib = sha256()
    new_hash_lib.update(concatenated)
    new_digest = new_hash_lib.digest()
    return new_digest

Esegui l'esempio completo di codice

Eseguite l'esempio di codice completo come segue per eseguire tutti i passaggi precedenti dall'inizio alla fine.

Java
import com.amazon.ion.IonBlob;
import com.amazon.ion.IonDatagram;
import com.amazon.ion.IonList;
import com.amazon.ion.IonReader;
import com.amazon.ion.IonString;
import com.amazon.ion.IonStruct;
import com.amazon.ion.IonSystem;
import com.amazon.ion.IonValue;
import com.amazon.ion.system.IonSystemBuilder;
import com.amazonaws.services.qldb.AmazonQLDB;
import com.amazonaws.services.qldb.AmazonQLDBClientBuilder;
import com.amazonaws.services.qldb.model.GetBlockRequest;
import com.amazonaws.services.qldb.model.GetBlockResult;
import com.amazonaws.services.qldb.model.GetDigestRequest;
import com.amazonaws.services.qldb.model.GetDigestResult;
import com.amazonaws.services.qldb.model.GetRevisionRequest;
import com.amazonaws.services.qldb.model.GetRevisionResult;
import com.amazonaws.services.qldb.model.ValueHolder;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import java.util.ListIterator;

import software.amazon.awssdk.regions.Region;
import software.amazon.awssdk.services.qldbsession.QldbSessionClient;
import software.amazon.awssdk.services.qldbsession.QldbSessionClientBuilder;
import software.amazon.qldb.QldbDriver;
import software.amazon.qldb.Result;

public class BlockHashVerification {
    private static final IonSystem SYSTEM = IonSystemBuilder.standard().build();
    private static final QldbDriver driver = createQldbDriver();
    private static final AmazonQLDB client = AmazonQLDBClientBuilder.standard().build();
    private static final String region = "us-east-1";
    private static final String ledgerName = "vehicle-registration";
    private static final String tableName = "VehicleRegistration";
    private static final String vin = "KM8SRDHF6EU074761";
    private static final int HASH_LENGTH = 32;

    /**
     * Create a pooled driver for creating sessions.
     *
     * @return The pooled driver for creating sessions.
     */
    public static QldbDriver createQldbDriver() {
        QldbSessionClientBuilder sessionClientBuilder = QldbSessionClient.builder();
        sessionClientBuilder.region(Region.of(region));

        return QldbDriver.builder()
                .ledger(ledgerName)
                .sessionClientBuilder(sessionClientBuilder)
                .build();
    }

    /**
     * Takes two hashes, sorts them, concatenates them, and then returns the
     * hash of the concatenated array.
     *
     * @param h1
     *              Byte array containing one of the hashes to compare.
     * @param h2
     *              Byte array containing one of the hashes to compare.
     * @return the concatenated array of hashes.
     */
    public static byte[] dot(final byte[] h1, final byte[] h2) {
        if (h1.length != HASH_LENGTH || h2.length != HASH_LENGTH) {
            throw new IllegalArgumentException("Invalid hash.");
        }

        int byteEqual = 0;
        for (int i = h1.length - 1; i >= 0; i--) {
            byteEqual = Byte.compare(h1[i], h2[i]);
            if (byteEqual != 0) {
                break;
            }
        }

        byte[] concatenated = new byte[h1.length + h2.length];
        if (byteEqual < 0) {
            System.arraycopy(h1, 0, concatenated, 0, h1.length);
            System.arraycopy(h2, 0, concatenated, h1.length, h2.length);
        } else {
            System.arraycopy(h2, 0, concatenated, 0, h2.length);
            System.arraycopy(h1, 0, concatenated, h2.length, h1.length);
        }

        MessageDigest messageDigest;
        try {
            messageDigest = MessageDigest.getInstance("SHA-256");
        } catch (NoSuchAlgorithmException e) {
            throw new IllegalStateException("SHA-256 message digest is unavailable", e);
        }

        messageDigest.update(concatenated);
        return messageDigest.digest();
    }

    public static void main(String[] args) {
        // Get a digest
        GetDigestRequest digestRequest = new GetDigestRequest().withName(ledgerName);
        GetDigestResult digestResult = client.getDigest(digestRequest);

        java.nio.ByteBuffer digest = digestResult.getDigest();

        // expectedDigest is the buffer we will use later to compare against our calculated digest
        byte[] expectedDigest = new byte[digest.remaining()];
        digest.get(expectedDigest);

        // Retrieve info for the given vin's document revisions
        Result result = driver.execute(txn -> {
            final String query = String.format("SELECT blockAddress, hash, metadata.id FROM _ql_committed_%s WHERE data.VIN = '%s'", tableName, vin);
            return txn.execute(query);
        });

        System.out.printf("Verifying document revisions for vin '%s' in table '%s' in ledger '%s'%n", vin, tableName, ledgerName);

        for (IonValue ionValue : result) {
            IonStruct ionStruct = (IonStruct)ionValue;

            // Get the requested fields
            IonValue blockAddress = ionStruct.get("blockAddress");
            IonBlob hash = (IonBlob)ionStruct.get("hash");
            String metadataId = ((IonString)ionStruct.get("id")).stringValue();

            System.out.printf("Verifying document revision for id '%s'%n", metadataId);

            String blockAddressText = blockAddress.toString();

            // Submit a request for the revision
            GetRevisionRequest revisionRequest = new GetRevisionRequest()
                    .withName(ledgerName)
                    .withBlockAddress(new ValueHolder().withIonText(blockAddressText))
                    .withDocumentId(metadataId)
                    .withDigestTipAddress(digestResult.getDigestTipAddress());

            // Get a result back
            GetRevisionResult revisionResult = client.getRevision(revisionRequest);

            String proofText = revisionResult.getProof().getIonText();

            // Take the proof and convert it to a list of byte arrays
            List<byte[]> internalHashes = new ArrayList<>();
            IonReader reader = SYSTEM.newReader(proofText);
            reader.next();
            reader.stepIn();
            while (reader.next() != null) {
                internalHashes.add(reader.newBytes());
            }

            // Calculate digest
            byte[] calculatedDigest = internalHashes.stream().reduce(hash.getBytes(), BlockHashVerification::dot);

            boolean verified = Arrays.equals(expectedDigest, calculatedDigest);

            if (verified) {
                System.out.printf("Successfully verified document revision for id '%s'!%n", metadataId);
            } else {
                System.out.printf("Document revision for id '%s' verification failed!%n", metadataId);
                return;
            }

            // Submit a request for the block
            GetBlockRequest getBlockRequest = new GetBlockRequest()
                    .withName(ledgerName)
                    .withBlockAddress(new ValueHolder().withIonText(blockAddressText))
                    .withDigestTipAddress(digestResult.getDigestTipAddress());

            // Get a result back
            GetBlockResult getBlockResult = client.getBlock(getBlockRequest);

            String blockText = getBlockResult.getBlock().getIonText();

            IonDatagram datagram = SYSTEM.getLoader().load(blockText);
            ionStruct = (IonStruct)datagram.get(0);

            final byte[] blockHash = ((IonBlob)ionStruct.get("blockHash")).getBytes();

            proofText = getBlockResult.getProof().getIonText();

            // Take the proof and create a list of hash binary data
            datagram = SYSTEM.getLoader().load(proofText);
            ListIterator<IonValue> listIter = ((IonList)datagram.iterator().next()).listIterator();

            internalHashes.clear();
            while (listIter.hasNext()) {
                internalHashes.add(((IonBlob)listIter.next()).getBytes());
            }

            // Calculate digest
            calculatedDigest = internalHashes.stream().reduce(blockHash, BlockHashVerification::dot);

            verified = Arrays.equals(expectedDigest, calculatedDigest);

            if (verified) {
                System.out.printf("Block address '%s' successfully verified!%n", blockAddressText);
            } else {
                System.out.printf("Block address '%s' verification failed!%n", blockAddressText);
            }
        }
    }
}
.NET
using Amazon.IonDotnet;
using Amazon.IonDotnet.Builders;
using Amazon.IonDotnet.Tree;
using Amazon.QLDB;
using Amazon.QLDB.Driver;
using Amazon.QLDB.Model;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Security.Cryptography;

namespace BlockHashVerification
{
    class BlockHashVerification
    {
        private static readonly string ledgerName = "vehicle-registration";
        private static readonly string tableName = "VehicleRegistration";
        private static readonly string vin = "KM8SRDHF6EU074761";
        private static readonly IQldbDriver driver = QldbDriver.Builder().WithLedger(ledgerName).Build();
        private static readonly IAmazonQLDB client = new AmazonQLDBClient();

        /// <summary>
        /// Takes two hashes, sorts them, concatenates them, and then returns the
        /// hash of the concatenated array.
        /// </summary>
        /// <param name="h1">Byte array containing one of the hashes to compare.</param>
        /// <param name="h2">Byte array containing one of the hashes to compare.</param>
        /// <returns>The concatenated array of hashes.</returns>
        private static byte[] Dot(byte[] h1, byte[] h2)
        {
            if (h1.Length == 0)
            {
                return h2;
            }

            if (h2.Length == 0)
            {
                return h1;
            }

            HashAlgorithm hashAlgorithm = HashAlgorithm.Create("SHA256");
            HashComparer comparer = new HashComparer();
            if (comparer.Compare(h1, h2) < 0)
            {
                return hashAlgorithm.ComputeHash(h1.Concat(h2).ToArray());
            }
            else
            {
                return hashAlgorithm.ComputeHash(h2.Concat(h1).ToArray());
            }
        }

        private class HashComparer : IComparer<byte[]>
        {
            private static readonly int HASH_LENGTH = 32;

            public int Compare(byte[] h1, byte[] h2)
            {
                if (h1.Length != HASH_LENGTH || h2.Length != HASH_LENGTH)
                {
                    throw new ArgumentException("Invalid hash");
                }

                for (var i = h1.Length - 1; i >= 0; i--)
                {
                    var byteEqual = (sbyte)h1[i] - (sbyte)h2[i];
                    if (byteEqual != 0)
                    {
                        return byteEqual;
                    }
                }

                return 0;
            }
        }

        static void Main()
        {
            // Get a digest
            GetDigestRequest getDigestRequest = new GetDigestRequest
            {
                Name = ledgerName
            };
            GetDigestResponse getDigestResponse = client.GetDigestAsync(getDigestRequest).Result;

            // expectedDigest is the buffer we will use later to compare against our calculated digest
            MemoryStream digest = getDigestResponse.Digest;
            byte[] expectedDigest = digest.ToArray();

            // Retrieve info for the given vin's document revisions
            var result = driver.Execute(txn => {
                string query = $"SELECT blockAddress, hash, metadata.id FROM _ql_committed_{tableName} WHERE data.VIN = '{vin}'";
                return txn.Execute(query);
            });

            Console.WriteLine($"Verifying document revisions for vin '{vin}' in table '{tableName}' in ledger '{ledgerName}'");

            foreach (IIonValue ionValue in result)
            {
                IIonStruct ionStruct = ionValue;

                // Get the requested fields
                IIonValue blockAddress = ionStruct.GetField("blockAddress");
                IIonBlob hash = ionStruct.GetField("hash");
                String metadataId = ionStruct.GetField("id").StringValue;

                Console.WriteLine($"Verifying document revision for id '{metadataId}'");

                // Use an Ion Reader to convert block address to text
                IIonReader reader = IonReaderBuilder.Build(blockAddress);
                StringWriter sw = new StringWriter();
                IIonWriter textWriter = IonTextWriterBuilder.Build(sw);
                textWriter.WriteValues(reader);
                string blockAddressText = sw.ToString();

                // Submit a request for the revision
                GetRevisionRequest revisionRequest = new GetRevisionRequest
                {
                    Name = ledgerName,
                    BlockAddress = new ValueHolder
                    {
                        IonText = blockAddressText
                    },
                    DocumentId = metadataId,
                    DigestTipAddress = getDigestResponse.DigestTipAddress
                };
                
                // Get a response back
                GetRevisionResponse revisionResponse = client.GetRevisionAsync(revisionRequest).Result;

                string proofText = revisionResponse.Proof.IonText;
                IIonDatagram proofValue = IonLoader.Default.Load(proofText);

                byte[] documentHash = hash.Bytes().ToArray();
                foreach (IIonValue proofHash in proofValue.GetElementAt(0))
                {
                    // Calculate the digest
                    documentHash = Dot(documentHash, proofHash.Bytes().ToArray());
                }

                bool verified = expectedDigest.SequenceEqual(documentHash);

                if (verified)
                {
                    Console.WriteLine($"Successfully verified document revision for id '{metadataId}'!");
                }
                else
                {
                    Console.WriteLine($"Document revision for id '{metadataId}' verification failed!");
                    return;
                }

                // Submit a request for the block
                GetBlockRequest getBlockRequest = new GetBlockRequest
                {
                    Name = ledgerName,
                    BlockAddress = new ValueHolder
                    {
                        IonText = blockAddressText
                    },
                    DigestTipAddress = getDigestResponse.DigestTipAddress
                };

                // Get a response back
                GetBlockResponse getBlockResponse = client.GetBlockAsync(getBlockRequest).Result;

                string blockText = getBlockResponse.Block.IonText;
                IIonDatagram blockValue = IonLoader.Default.Load(blockText);

                // blockValue is a IonDatagram, and the first value is an IonStruct containing the blockHash
                byte[] blockHash = blockValue.GetElementAt(0).GetField("blockHash").Bytes().ToArray();

                proofText = getBlockResponse.Proof.IonText;
                proofValue = IonLoader.Default.Load(proofText);

                foreach (IIonValue proofHash in proofValue.GetElementAt(0))
                {
                    // Calculate the digest
                    blockHash = Dot(blockHash, proofHash.Bytes().ToArray());
                }

                verified = expectedDigest.SequenceEqual(blockHash);

                if (verified)
                {
                    Console.WriteLine($"Block address '{blockAddressText}' successfully verified!");
                }
                else
                {
                    Console.WriteLine($"Block address '{blockAddressText}' verification failed!");
                }
            }
        }
    }
}
Go
package main

import (
    "context"
    "crypto/sha256"
    "errors"
    "fmt"
    "reflect"

    "github.com/amzn/ion-go/ion"
    "github.com/aws/aws-sdk-go/aws"
    AWSSession "github.com/aws/aws-sdk-go/aws/session"
    "github.com/aws/aws-sdk-go/service/qldb"
    "github.com/aws/aws-sdk-go/service/qldbsession"
    "github.com/awslabs/amazon-qldb-driver-go/qldbdriver"
)

const (
    hashLength = 32
    ledgerName = "vehicle-registration"
    tableName  = "VehicleRegistration"
    vin        = "KM8SRDHF6EU074761"
)

// Takes two hashes, sorts them, concatenates them, and then returns the hash of the concatenated array.
func dot(h1, h2 []byte) ([]byte, error) {
    compare, err := hashComparator(h1, h2)
    if err != nil {
        return nil, err
    }

    var concatenated []byte
    if compare < 0 {
        concatenated = append(h1, h2...)
    } else {
        concatenated = append(h2, h1...)
    }

    newHash := sha256.Sum256(concatenated)
    return newHash[:], nil
}

func hashComparator(h1 []byte, h2 []byte) (int16, error) {
    if len(h1) != hashLength || len(h2) != hashLength {
        return 0, errors.New("invalid hash")
    }
    for i := range h1 {
        // Reverse index for little endianness
        index := hashLength - 1 - i

        // Handle byte being unsigned and overflow
        h1Int := int16(h1[index])
        h2Int := int16(h2[index])
        if h1Int > 127 {
            h1Int = 0 - (256 - h1Int)
        }
        if h2Int > 127 {
            h2Int = 0 - (256 - h2Int)
        }

        difference := h1Int - h2Int
        if difference != 0 {
            return difference, nil
        }
    }
    return 0, nil
}

func main() {
    driverSession := AWSSession.Must(AWSSession.NewSession(aws.NewConfig()))
    qldbSession := qldbsession.New(driverSession)
    driver, err := qldbdriver.New(ledgerName, qldbSession, func(options *qldbdriver.DriverOptions) {})
    if err != nil {
        panic(err)
    }
    client := qldb.New(driverSession)

    // Get a digest
    currentLedgerName := ledgerName
    input := qldb.GetDigestInput{Name: &currentLedgerName}
    digestOutput, err := client.GetDigest(&input)
    if err != nil {
        panic(err)
    }

    // expectedDigest is the buffer we will later use to compare against our calculated digest
    expectedDigest := digestOutput.Digest

    // Retrieve info for the given vin's document revisions
    result, err := driver.Execute(context.Background(), func(txn qldbdriver.Transaction) (interface{}, error) {
        statement := fmt.Sprintf(
                "SELECT blockAddress, hash, metadata.id FROM _ql_committed_%s WHERE data.VIN = '%s'",
                tableName,
                vin)
        result, err := txn.Execute(statement)
        if err != nil {
            return nil, err
        }

        results := make([]map[string]interface{}, 0)

        // Convert the result set into a map
        for result.Next(txn) {
            var doc map[string]interface{}
            err := ion.Unmarshal(result.GetCurrentData(), &doc)
            if err != nil {
                return nil, err
            }
            results = append(results, doc)
        }
        return results, nil
    })
    if err != nil {
        panic(err)
    }
    resultSlice := result.([]map[string]interface{})

    fmt.Printf("Verifying document revisions for vin '%s' in table '%s' in ledger '%s'\n", vin, tableName, ledgerName)

    for _, value := range resultSlice {
        // Get the requested fields
        ionBlockAddress, err := ion.MarshalText(value["blockAddress"])
        if err != nil {
            panic(err)
        }
        blockAddress := string(ionBlockAddress)
        metadataId := value["id"].(string)
        documentHash := value["hash"].([]byte)

        fmt.Printf("Verifying document revision for id '%s'\n", metadataId)

        // Submit a request for the revision
        revisionInput := qldb.GetRevisionInput{
            BlockAddress:     &qldb.ValueHolder{IonText: &blockAddress},
            DigestTipAddress: digestOutput.DigestTipAddress,
            DocumentId:       &metadataId,
            Name:             &currentLedgerName,
        }

        // Get a result back
        revisionOutput, err := client.GetRevision(&revisionInput)
        if err != nil {
            panic(err)
        }

        proofText := revisionOutput.Proof.IonText

        // Use ion.Reader to iterate over the proof's node hashes
        reader := ion.NewReaderString(*proofText)
        // Enter the struct containing node hashes
        reader.Next()
        if err := reader.StepIn(); err != nil {
            panic(err)
        }

        // Going through nodes and calculate digest
        for reader.Next() {
            val, _ := reader.ByteValue()
            documentHash, err = dot(documentHash, val)
        }

        // Compare documentHash with the expected digest
        verified := reflect.DeepEqual(documentHash, expectedDigest)

        if verified {
            fmt.Printf("Successfully verified document revision for id '%s'!\n", metadataId)
        } else {
            fmt.Printf("Document revision for id '%s' verification failed!\n", metadataId)
            return
        }

        // Submit a request for the block
        blockInput := qldb.GetBlockInput{
            Name:             &currentLedgerName,
            BlockAddress:     &qldb.ValueHolder{IonText: &blockAddress},
            DigestTipAddress: digestOutput.DigestTipAddress,
        }

        // Get a result back
        blockOutput, err := client.GetBlock(&blockInput)
        if err != nil {
            panic(err)
        }

        proofText = blockOutput.Proof.IonText

        block := new(map[string]interface{})
        err = ion.UnmarshalString(*blockOutput.Block.IonText, block)
        if err != nil {
            panic(err)
        }

        blockHash := (*block)["blockHash"].([]byte)

        // Use ion.Reader to iterate over the proof's node hashes
        reader = ion.NewReaderString(*proofText)
        // Enter the struct containing node hashes
        reader.Next()
        if err := reader.StepIn(); err != nil {
            panic(err)
        }

        // Going through nodes and calculate digest
        for reader.Next() {
            val, err := reader.ByteValue()
            if err != nil {
                panic(err)
            }
            blockHash, err = dot(blockHash, val)
        }

        // Compare blockHash with the expected digest
        verified = reflect.DeepEqual(blockHash, expectedDigest)

        if verified {
            fmt.Printf("Block address '%s' successfully verified!\n", blockAddress)
        } else {
            fmt.Printf("Block address '%s' verification failed!\n", blockAddress)
            return
        }
    }
}
Node.js
import { QldbDriver, Result, TransactionExecutor} from "amazon-qldb-driver-nodejs";
import { QLDB } from "aws-sdk"
import { GetBlockRequest, GetBlockResponse, GetDigestRequest, GetDigestResponse, GetRevisionRequest, GetRevisionResponse } from "aws-sdk/clients/qldb";
import { createHash } from "crypto";
import { dom, dumpText, load } from "ion-js"

const ledgerName: string = "vehicle-registration";
const tableName: string = "VehicleRegistration";
const vin: string = "KM8SRDHF6EU074761";
const driver: QldbDriver = new QldbDriver(ledgerName);
const qldbClient: QLDB = new QLDB();
const HASH_SIZE = 32;

/**
 * Takes two hashes, sorts them, concatenates them, and calculates a digest based on the concatenated hash.
 * @param h1 Byte array containing one of the hashes to compare.
 * @param h2 Byte array containing one of the hashes to compare.
 * @returns The digest calculated from the concatenated hash values.
 */
function dot(h1: Uint8Array, h2: Uint8Array): Uint8Array {
    if (h1.length === 0) {
        return h2;
    }
    if (h2.length === 0) {
        return h1;
    }

    const newHashLib = createHash("sha256");

    let concatenated: Uint8Array;
    if (hashComparator(h1, h2) < 0) {
        concatenated = concatenate(h1, h2);
    } else {
        concatenated = concatenate(h2, h1);
    }
    newHashLib.update(concatenated);
    return newHashLib.digest();
}

/**
 * Compares two hashes by their **signed** byte values in little-endian order.
 * @param hash1 The hash value to compare.
 * @param hash2 The hash value to compare.
 * @returns Zero if the hash values are equal, otherwise return the difference of the first pair of non-matching
 *          bytes.
 * @throws RangeError When the hash is not the correct hash size.
 */
function hashComparator(hash1: Uint8Array, hash2: Uint8Array): number {
    if (hash1.length !== HASH_SIZE || hash2.length !== HASH_SIZE) {
        throw new RangeError("Invalid hash.");
    }
    for (let i = hash1.length-1; i >= 0; i--) {
        const difference: number = (hash1[i]<<24 >>24) - (hash2[i]<<24 >>24);
        if (difference !== 0) {
            return difference;
        }
    }
    return 0;
}

/**
 * Helper method that concatenates two Uint8Array.
 * @param arrays List of arrays to concatenate, in the order provided.
 * @returns The concatenated array.
 */
function concatenate(...arrays: Uint8Array[]): Uint8Array {
    let totalLength = 0;
    for (const arr of arrays) {
        totalLength += arr.length;
    }
    const result = new Uint8Array(totalLength);
    let offset = 0;
    for (const arr of arrays) {
        result.set(arr, offset);
        offset += arr.length;
    }
    return result;
}

/**
 * Helper method that checks for equality between two Uint8Array.
 * @param expected Byte array containing one of the hashes to compare.
 * @param actual Byte array containing one of the hashes to compare.
 * @returns Boolean indicating equality between the two Uint8Array.
 */
function isEqual(expected: Uint8Array, actual: Uint8Array): boolean {
    if (expected === actual) return true;
    if (expected == null || actual == null) return false;
    if (expected.length !== actual.length) return false;

    for (let i = 0; i < expected.length; i++) {
        if (expected[i] !== actual[i]) {
            return false;
        }
    }
    return true;
}

const main = async function (): Promise<void> {
    // Get a digest
    const getDigestRequest: GetDigestRequest = {
        Name: ledgerName
    };
    const getDigestResponse: GetDigestResponse = await qldbClient.getDigest(getDigestRequest).promise();

    // expectedDigest is the buffer we will later use to compare against our calculated digest
    const expectedDigest: Uint8Array = <Uint8Array>getDigestResponse.Digest;

    const result: dom.Value[] = await driver.executeLambda(async (txn: TransactionExecutor): Promise<dom.Value[]> => {
        const query: string = `SELECT blockAddress, hash, metadata.id FROM _ql_committed_${tableName} WHERE data.VIN = '${vin}'`;
        const queryResult: Result = await txn.execute(query);
        return queryResult.getResultList();
    });

    console.log(`Verifying document revisions for vin '${vin}' in table '${tableName}' in ledger '${ledgerName}'`);

    for (let value of result) {
        // Get the requested fields
        const blockAddress: dom.Value = value.get("blockAddress");
        const hash: dom.Value = value.get("hash");
        const metadataId: string = value.get("id").stringValue();

        console.log(`Verifying document revision for id '${metadataId}'`);

        // Submit a request for the revision
        const revisionRequest: GetRevisionRequest = {
            Name: ledgerName,
            BlockAddress: {
                IonText: dumpText(blockAddress)
            },
            DocumentId: metadataId,
            DigestTipAddress: getDigestResponse.DigestTipAddress
        };

        // Get a response back
        const revisionResponse: GetRevisionResponse = await qldbClient.getRevision(revisionRequest).promise();

        let proofValue: dom.Value = load(revisionResponse.Proof.IonText);

        let documentHash: Uint8Array = hash.uInt8ArrayValue();
        proofValue.elements().forEach((proofHash: dom.Value) => {
            // Calculate the digest
            documentHash = dot(documentHash, proofHash.uInt8ArrayValue());
        });

        let verified: boolean = isEqual(expectedDigest, documentHash);

        if (verified) {
            console.log(`Successfully verified document revision for id '${metadataId}'!`);
        } else {
            console.log(`Document revision for id '${metadataId}' verification failed!`);
            return;
        }

        // Submit a request for the block
        const getBlockRequest: GetBlockRequest = {
            Name: ledgerName,
            BlockAddress: {
                IonText: dumpText(blockAddress)
            },
            DigestTipAddress: getDigestResponse.DigestTipAddress
        };

        // Get a response back
        const getBlockResponse: GetBlockResponse = await qldbClient.getBlock(getBlockRequest).promise();

        const blockValue: dom.Value = load(getBlockResponse.Block.IonText)
        let blockHash: Uint8Array = blockValue.get("blockHash").uInt8ArrayValue();

        proofValue = load(getBlockResponse.Proof.IonText);

        proofValue.elements().forEach((proofHash: dom.Value) => {
            // Calculate the digest
            blockHash = dot(blockHash, proofHash.uInt8ArrayValue());
        });

        verified = isEqual(expectedDigest, blockHash);

        if (verified) {
            console.log(`Block address '${dumpText(blockAddress)}' successfully verified!`);
        } else {
            console.log(`Block address '${dumpText(blockAddress)}' verification failed!`);
        }
    }
};

if (require.main === module) {
    main();
}
Python
from amazon.ion.simpleion import dumps, loads
from array import array
from boto3 import client
from functools import reduce
from hashlib import sha256
from pyqldb.driver.qldb_driver import QldbDriver

ledger_name = 'vehicle-registration'
table_name = 'VehicleRegistration'
vin = 'KM8SRDHF6EU074761'
qldb_client = client('qldb')
hash_length = 32


def query_doc_revision(txn):
    query = "SELECT blockAddress, hash, metadata.id FROM _ql_committed_{} WHERE data.VIN = '{}'".format(table_name, vin)
    return txn.execute_statement(query)


def block_address_to_dictionary(ion_dict):
    """
    Convert a block address from IonPyDict into a dictionary.
    Shape of the dictionary must be: {'IonText': "{strandId: <"strandId">, sequenceNo: <sequenceNo>}"}

    :type ion_dict: :py:class:`amazon.ion.simple_types.IonPyDict`/str
    :param ion_dict: The block address value to convert.

    :rtype: dict
    :return: The converted dict.
    """
    block_address = {'IonText': {}}
    if not isinstance(ion_dict, str):
        py_dict = '{{strandId: "{}", sequenceNo:{}}}'.format(ion_dict['strandId'], ion_dict['sequenceNo'])
        ion_dict = py_dict
    block_address['IonText'] = ion_dict
    return block_address


def dot(hash1, hash2):
    """
    Takes two hashes, sorts them, concatenates them, and then returns the
    hash of the concatenated array.

    :type hash1: bytes
    :param hash1: The hash value to compare.

    :type hash2: bytes
    :param hash2: The hash value to compare.

    :rtype: bytes
    :return: The new hash value generated from concatenated hash values.
    """
    if len(hash1) != hash_length or len(hash2) != hash_length:
        raise ValueError('Illegal hash.')

    hash_array1 = array('b', hash1)
    hash_array2 = array('b', hash2)

    difference = 0
    for i in range(len(hash_array1) - 1, -1, -1):
        difference = hash_array1[i] - hash_array2[i]
        if difference != 0:
            break

    if difference < 0:
        concatenated = hash1 + hash2
    else:
        concatenated = hash2 + hash1

    new_hash_lib = sha256()
    new_hash_lib.update(concatenated)
    new_digest = new_hash_lib.digest()
    return new_digest


# Get a digest
get_digest_response = qldb_client.get_digest(Name=ledger_name)

# expected_digest is the buffer we will later use to compare against our calculated digest
expected_digest = get_digest_response.get('Digest')
digest_tip_address = get_digest_response.get('DigestTipAddress')

qldb_driver = QldbDriver(ledger_name=ledger_name)

# Retrieve info for the given vin's document revisions
result = qldb_driver.execute_lambda(query_doc_revision)

print("Verifying document revisions for vin '{}' in table '{}' in ledger '{}'".format(vin, table_name, ledger_name))

for value in result:
    # Get the requested fields
    block_address = value['blockAddress']
    document_hash = value['hash']
    metadata_id = value['id']

    print("Verifying document revision for id '{}'".format(metadata_id))

    # Submit a request for the revision and get a result back
    proof_response = qldb_client.get_revision(Name=ledger_name,
                                              BlockAddress=block_address_to_dictionary(block_address),
                                              DocumentId=metadata_id,
                                              DigestTipAddress=digest_tip_address)

    proof_text = proof_response.get('Proof').get('IonText')
    proof_hashes = loads(proof_text)

    # Calculate digest
    calculated_digest = reduce(dot, proof_hashes, document_hash)

    verified = calculated_digest == expected_digest
    if verified:
        print("Successfully verified document revision for id '{}'!".format(metadata_id))
    else:
        print("Document revision for id '{}' verification failed!".format(metadata_id))

    # Submit a request for the block and get a result back
    block_response = qldb_client.get_block(Name=ledger_name, BlockAddress=block_address_to_dictionary(block_address),
                                           DigestTipAddress=digest_tip_address)

    block_text = block_response.get('Block').get('IonText')
    block = loads(block_text)

    block_hash = block.get('blockHash')

    proof_text = block_response.get('Proof').get('IonText')
    proof_hashes = loads(proof_text)

    # Calculate digest
    calculated_digest = reduce(dot, proof_hashes, block_hash)

    verified = calculated_digest == expected_digest
    if verified:
        print("Block address '{}' successfully verified!".format(dumps(block_address,
                                                                       binary=False,
                                                                       omit_version_marker=True)))
    else:
        print("Block address '{}' verification failed!".format(block_address))