자습서: a를 사용하여 데이터 확인하기 AWS SDK - 아마존 퀀텀 레저 데이터베이스 (아마존QLDB)
사전 조건1단계: 다이제스트 요청2단계: 문서 수정본 쿼리3단계: 수정에 대한 증명 요청4단계: 수정본에서 다이제스트 다시 계산하기5단계: 저널 블록에 대한 증명 요청6단계: 블록의 다이제스트 다시 계산하기전체 코드 예제 실행

기계 번역으로 제공되는 번역입니다. 제공된 번역과 원본 영어의 내용이 상충하는 경우에는 영어 버전이 우선합니다.

자습서: a를 사용하여 데이터 확인하기 AWS SDK

중요

지원 종료 알림: 기존 고객은 2025년 7월 31일 지원이 종료될 QLDB 때까지 Amazon을 사용할 수 있습니다. 자세한 내용은 아마존 QLDB 원장을 Amazon Aurora SQL Postgre로 마이그레이션을 참조하십시오.

이 자습서에서는 다음을 사용하여 Amazon QLDB 원장의 문서 수정 해시와 저널 블록 해시를 확인합니다. QLDB API AWS SDK. QLDB드라이버를 사용하여 문서 개정을 쿼리할 수도 있습니다.

예를 들어 차량 식별 번호 (VIN) 가 인 차량에 대한 데이터가 포함된 문서 개정판이 있다고 가정해 보겠습니다KM8SRDHF6EU074761. 문서 수정본은 vehicle-registration라는 이름의 원장에 있는 VehicleRegistration 테이블에 있습니다. 이 차량에 대한 문서 수정본과 수정본이 포함된 저널 블록 모두의 무결성을 확인한다고 가정해 보겠습니다.

참고

자세한 내용은 AWS 실제 사용 사례의 맥락에서 암호화 검증의 가치를 설명하는 블로그 게시물은 Amazon을 사용한 실제 암호화 검증을 참조하십시오. QLDB

사전 조건

시작하기 전에 다음을 수행해야 합니다.

  1. 에서 각 사전 요구 사항을 완료하여 원하는 언어에 맞는 QLDB 드라이버를 설정하십시오. Amazon QLDB 드라이버 시작하기 여기에는 다음에 대한 가입이 포함됩니다. AWS, 개발을 위한 프로그래밍 액세스 권한 부여 및 개발 환경 구성.

  2. Amazon QLDB 콘솔 시작하기의 1~2단계에 따라 vehicle-registration라는 이름의 원장을 생성하고 사전 정의된 샘플 데이터와 함께 로드하세요.

그런 다음, 다음 단계를 검토하여 확인 작동 방식을 알아본 다음 전체 코드 예제를 처음부터 끝까지 실행합니다.

1단계: 다이제스트 요청

데이터를 확인하려면 먼저 나중에 사용할 수 있도록 원장 vehicle-registration에 다이제스트를 요청해야 합니다.

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')

2단계: 문서 수정본 쿼리

QLDB드라이버를 사용하여 관련된 블록 주소, 해시 및 문서를 IDs 쿼리할 수 있습니다. 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)

3단계: 수정에 대한 증명 요청

쿼리 결과를 반복해서 살펴보고 각 블록 주소 및 문서 ID를 원장 이름과 함께 사용하여 GetRevision 요청을 제출합니다. 수정에 대한 증명을 가져오려면 이전에 저장한 다이제스트의 팁 주소도 제공해야 합니다. 이 API 작업을 수행하면 문서 개정과 개정 증명이 포함된 객체가 반환됩니다.

저널 블록 구조 및 내용에 대한 자세한 내용은 문서 메타데이터 쿼리 섹션을 참조하세요.

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)

그런 다음 요청된 수정본에 대한 증명을 검색하세요.

는 정렬된 노드 해시 목록을 문자열로 표현하여 증명을 QLDB API 반환합니다. 이 문자열을 노드 해시의 이진수 표현 목록으로 변환하려면 Amazon Ion 라이브러리의 Ion 리더를 사용합니다. Ion 라이브러리 사용에 대한 자세한 내용은 Amazon Ion Cookbook을 참조하세요.

Java

이 예제에서는 IonReader를 사용하여 이진수 변환을 수행합니다.

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

이 예제에서는 IonLoader를 사용하여 증명을 Ion 데이터그램으로 로드합니다.

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

이 예제에서는 Ion 리더를 사용하여 증명을 이진수로 변환하고 증명의 노드 해시 목록을 반복해서 살펴봅니다.

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

이 예제에서는 load 함수를 사용하여 이진 변환을 수행합니다.

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

이 예제에서는 loads 함수를 사용하여 이진 변환을 수행합니다.

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

4단계: 수정본에서 다이제스트 다시 계산하기

증명의 해시 목록을 사용하여 수정 해시부터 시작하여 다이제스트를 다시 계산합니다. 이전에 저장한 다이제스트를 외부에서 알고 신뢰할 수 있는 한QLDB, 재계산된 다이제스트 해시가 저장된 다이제스트 해시와 일치하면 문서 개정의 무결성이 입증됩니다.

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))

5단계: 저널 블록에 대한 증명 요청

다음으로, 문서 수정본이 포함된 저널 블록을 확인합니다.

1단계에서 저장한 다이제스트의 블록 주소와 팁 주소를 사용하여 GetBlock 요청을 제출합니다. 2단계의 GetRevision 요청과 마찬가지로, 저장된 다이제스트의 팁 주소를 다시 입력해야 블록에 대한 증명을 받을 수 있습니다. 이 API 작업을 수행하면 블록과 블록 증명이 포함된 객체가 반환됩니다.

저널 블록 구조 및 콘텐츠에 대한 자세한 콘텐츠는 아마존의 저널 콘텐츠 QLDB 섹션을 참조하세요.

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)

그런 다음 결과에서 블록 해시와 증명을 검색합니다.

Java

이 예제에서는 IonLoader를 사용하여 블록 객체를 IonDatagram 컨테이너에 로드합니다.

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

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

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

IonLoader를 사용하여 증명을 IonDatagram에 로드할 수도 있습니다.

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

이 예제에서는 IonLoader를 사용하여 블록과 증명을 각각의 Ion 데이터그램에 로드합니다.

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

이 예제에서는 Ion 리더를 사용하여 증명을 이진수로 변환하고 증명의 노드 해시 목록을 반복해서 살펴봅니다.

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

이 예제에서는 load 함수를 사용하여 블록과 증명을 이진수로 변환합니다.

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

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

이 예제에서는 loads 함수를 사용하여 블록과 증명을 이진수로 변환합니다.

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)

6단계: 블록의 다이제스트 다시 계산하기

증명의 해시 목록을 사용하여 블록 해시부터 시작하여 다이제스트를 다시 계산합니다. 이전에 저장된 다이제스트를 외부에서 알고 신뢰할 수 있는 한QLDB, 다시 계산된 다이제스트 해시가 저장된 다이제스트 해시와 일치하면 블록의 무결성이 입증됩니다.

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))

이전 코드 예제에서는 다이제스트를 다시 계산할 때 dot 함수를 사용합니다. 이 함수는 두 해시를 입력받아 두 해시를 정렬하고 연결한 다음 연결된 배열의 해시를 반환합니다.

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

전체 코드 예제 실행

다음과 같이 전체 코드 예제를 실행하여 이전 단계를 처음부터 끝까지 모두 수행합니다.

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))