Tutorial: Verifying data using an AWS SDK - Amazon Quantum Ledger Database (Amazon QLDB)

Tutorial: Verifying data using an AWS SDK

In this tutorial, you verify a document revision hash and a journal block hash in an Amazon QLDB ledger by using the QLDB API through an AWS SDK. You also use the QLDB driver to query the document revision.

Consider an example where you have a document revision that contains data for a vehicle with a vehicle identification number (VIN) of KM8SRDHF6EU074761. The document revision is in a VehicleRegistration table that is in a ledger named vehicle-registration. Suppose that you want to verify the integrity of both the document revision for this vehicle and the journal block that contains the revision.

Note

For a detailed AWS blog post that discusses the value of cryptographic verification in the context of a realistic use case, see Real-world cryptographic verification with Amazon QLDB.

Prerequisites

Before you get started, make sure that you do the following:

  1. Set up the QLDB driver for a language of your choice by completing the respective prerequisites under Getting started with the Amazon QLDB driver. This includes signing up for AWS, getting an IAM access key for development, and configuring your development environment.

  2. Follow steps 1–2 in Getting started with the Amazon QLDB console to create a ledger named vehicle-registration and load it with predefined sample data.

Next, review the following steps to learn how verification works, and then run the full code example from start to end.

Step 1: Request a digest

Before you can verify data, you must first request a digest from your ledger vehicle-registration for use later.

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')

Step 2: Query the document revision

Use the QLDB driver to query the block addresses, hashes, and document IDs that are associated with 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)

Step 3: Request a proof for the revision

Iterate through the query results and use each block address and document ID along with the ledger name to submit a GetRevision request. To get a proof for the revision, you must also provide the tip address from the previously saved digest. This API operation returns an object that includes the document revision and the proof for the revision.

For information about the revision structure and its contents, see Querying document metadata.

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)

Then, retrieve the proof for the requested revision.

The QLDB API returns the proof as a string representation of the ordered list of node hashes. To convert this string into a list of the binary representation of the node hashes, you can use an Ion reader from the Amazon Ion library. For more information about using the Ion library, see the Amazon Ion Cookbook.

Java

In this example, you use IonReader to do the binary conversion.

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 this example, you use IonLoader to load the proof into an Ion datagram.

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

In this example, you use an Ion reader to convert the proof to binary and to iterate through the proof's list of node hashes.

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 this example, you use the load function to do the binary conversion.

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

In this example, you use the loads function to do the binary conversion.

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

Step 4: Recalculate the digest from the revision

Use the proof's list of hashes to recalculate the digest, starting with the revision hash. As long as the previously saved digest is known and trusted outside of QLDB, the integrity of the document revision is proven if the recalculated digest hash matches the saved digest hash.

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))

Step 5: Request a proof for the journal block

Next, you verify the journal block that contains the document revision.

Use the block address and the tip address from the digest that you saved in Step 1 to submit a GetBlock request. Similar to the GetRevision request in Step 2, you must again provide the tip address from the saved digest to get a proof for the block. This API operation returns an object that includes the block and the proof for the block.

For information about the journal block structure and its contents, see Journal contents 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)

Then, retrieve the block hash and the proof from the result.

Java

In this example, you use IonLoader to load the block object into an IonDatagram container.

String blockText = getBlockResult.getBlock().getIonText(); IonDatagram datagram = SYSTEM.getLoader().load(blockText); ionStruct = (IonStruct)datagram.get(0); final byte[] blockHash = ((IonBlob)ionStruct.get("blockHash")).getBytes();

You also use IonLoader to load the proof into an IonDatagram.

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 this example, you use IonLoader to load the block and the proof into an Ion datagram for each.

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 this example, you use an Ion reader to convert the proof to binary and to iterate through the proof's list of node hashes.

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 this example, you use the load function to convert the block and the proof to binary.

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

In this example, you use the loads function to convert the block and the proof to binary.

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)

Step 6: Recalculate the digest from the block

Use the proof's list of hashes to recalculate the digest, starting with the block hash. As long as the previously saved digest is known and trusted outside of QLDB, the integrity of the block is proven if the recalculated digest hash matches the saved digest hash.

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))

The previous code examples use the following dot function when recalculating the digest. This function takes an input of two hashes, sorts them, concatenates them, and then returns the hash of the concatenated array.

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

Run the full code example

Run the full code example as follows to perform all of the preceding steps from start to end.

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))