第 7 步：验证分类账中的文档

重要

终止支持通知：现有客户将能够使用亚马逊，QLDB直到 2025 年 7 月 31 日终止支持。有关更多详细信息，请参阅将亚马逊QLDB账本迁移到亚马逊 Aurora Postgr SQL e。

借助 AmazonQLDB，您可以使用带有 -256 的加密哈希来有效地验证账本日记账中文档的完整性。SHA要详细了解验证和加密哈希的工作原理QLDB，请参阅。在 Amazon 中进行数据验证 QLDB

在此步骤中，您将验证 vehicle-registration 分类账 VehicleRegistration 表格中的单据修订版本。首先，您请求一份摘要，该摘要作为输出文件返回，并作为分类账整个变更历史记录的签名。然后，您要求提供与此摘要相关的修订证明。使用此证明，如果所有验证检查都可通过，可以验证修订版的完整性。

验证文档的修订版

查看以下.java文件，这些文件代表了验证所需的QLDB对象以及带有 Ion 和字符串值的辅助方法的实用程序类。

BlockAddress.java


/*
 * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: MIT-0
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package software.amazon.qldb.tutorial.qldb;

import java.util.Objects;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;

/**
 * Represents the BlockAddress field of a QLDB document.
 */
public final class BlockAddress {

    private static final Logger log = LoggerFactory.getLogger(BlockAddress.class);

    private final String strandId;
    private final long sequenceNo;

    @JsonCreator
    public BlockAddress(@JsonProperty("strandId") final String strandId,
                        @JsonProperty("sequenceNo") final long sequenceNo) {
        this.strandId = strandId;
        this.sequenceNo = sequenceNo;
    }

    public long getSequenceNo() {
        return sequenceNo;
    }

    public String getStrandId() {
        return strandId;
    }

    @Override
    public String toString() {
        return "BlockAddress{"
                + "strandId='" + strandId + '\''
                + ", sequenceNo=" + sequenceNo
                + '}';
    }

    @Override
    public boolean equals(final Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }
        BlockAddress that = (BlockAddress) o;
        return sequenceNo == that.sequenceNo
                && strandId.equals(that.strandId);
    }

    @Override
    public int hashCode() {
        // CHECKSTYLE:OFF - Disabling as we are generating a hashCode of multiple properties.
        return Objects.hash(strandId, sequenceNo);
        // CHECKSTYLE:ON
    }
}

Proof.java


/*
 * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: MIT-0
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package software.amazon.qldb.tutorial.qldb;

import com.amazon.ion.IonReader;
import com.amazon.ion.IonSystem;
import com.amazon.ion.system.IonSystemBuilder;
import com.amazonaws.services.qldb.model.GetRevisionRequest;
import com.amazonaws.services.qldb.model.GetRevisionResult;

import java.util.ArrayList;
import java.util.List;

/**
 * A Java representation of the {@link Proof} object.
 * Returned from the {@link com.amazonaws.services.qldb.AmazonQLDB#getRevision(GetRevisionRequest)} api.
 */
public final class Proof {
    private static final IonSystem SYSTEM = IonSystemBuilder.standard().build();

    private List<byte[]> internalHashes;

    public Proof(final List<byte[]> internalHashes) {
        this.internalHashes = internalHashes;
    }

    public List<byte[]> getInternalHashes() {
        return internalHashes;
    }

    /**
     * Decodes a {@link Proof} from an ion text String. This ion text is returned in
     * a {@link GetRevisionResult#getProof()}
     *
     * @param ionText
     *              The ion text representing a {@link Proof} object.
     * @return {@link JournalBlock} parsed from the ion text.
     * @throws IllegalStateException if failed to parse the {@link Proof} object from the given ion text.
     */
    public static Proof fromBlob(final String ionText) {
        try {
            IonReader reader = SYSTEM.newReader(ionText);
            List<byte[]> list = new ArrayList<>();
            reader.next();
            reader.stepIn();
            while (reader.next() != null) {
                list.add(reader.newBytes());
            }
            return new Proof(list);
        } catch (Exception e) {
            throw new IllegalStateException("Failed to parse a Proof from byte array");
        }
    }
}

QldbIonUtils.java


/*
 * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: MIT-0
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package software.amazon.qldb.tutorial.qldb;

import com.amazon.ion.IonReader;
import com.amazon.ion.IonValue;
import com.amazon.ionhash.IonHashReader;
import com.amazon.ionhash.IonHashReaderBuilder;
import com.amazon.ionhash.MessageDigestIonHasherProvider;
import software.amazon.qldb.tutorial.Constants;

public class QldbIonUtils {

    private static MessageDigestIonHasherProvider ionHasherProvider = new MessageDigestIonHasherProvider("SHA-256");

    private QldbIonUtils() {}

    /**
     * Builds a hash value from the given {@link IonValue}.
     *
     * @param ionValue
     *              The {@link IonValue} to hash.
     * @return a byte array representing the hash value.
     */
    public static byte[] hashIonValue(final IonValue ionValue) {
        IonReader reader = Constants.SYSTEM.newReader(ionValue);
        IonHashReader hashReader = IonHashReaderBuilder.standard()
                .withHasherProvider(ionHasherProvider)
                .withReader(reader)
                .build();
        while (hashReader.next() != null) {  }
        return hashReader.digest();
    }

}

QldbStringUtils.java


/*
 * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: MIT-0
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package software.amazon.qldb.tutorial.qldb;

import com.amazon.ion.IonWriter;
import com.amazon.ion.system.IonReaderBuilder;
import com.amazon.ion.system.IonTextWriterBuilder;
import com.amazonaws.services.qldb.model.GetBlockResult;
import com.amazonaws.services.qldb.model.GetDigestResult;
import com.amazonaws.services.qldb.model.ValueHolder;

import java.io.IOException;

/**
 * Helper methods to pretty-print certain QLDB response types.
 */
public class QldbStringUtils {

    private QldbStringUtils() {}

    /**
     * Returns the string representation of a given {@link ValueHolder}.
     * Adapted from the AWS SDK autogenerated {@code toString()} method, with sensitive values un-redacted.
     * Additionally, this method pretty-prints any IonText included in the {@link ValueHolder}.
     *
     * @param valueHolder the {@link ValueHolder} to convert to a String.
     * @return the String representation of the supplied {@link ValueHolder}.
     */
    public static String toUnredactedString(ValueHolder valueHolder) {
        StringBuilder sb = new StringBuilder();
        sb.append("{");
        if (valueHolder.getIonText() != null) {

            sb.append("IonText: ");
            IonWriter prettyWriter = IonTextWriterBuilder.pretty().build(sb);
            try {
                prettyWriter.writeValues(IonReaderBuilder.standard().build(valueHolder.getIonText()));
            } catch (IOException ioe) {
                sb.append("**Exception while printing this IonText**");
            }
        }

        sb.append("}");
        return sb.toString();
    }

    /**
     * Returns the string representation of a given {@link GetBlockResult}.
     * Adapted from the AWS SDK autogenerated {@code toString()} method, with sensitive values un-redacted.
     *
     * @param getBlockResult the {@link GetBlockResult} to convert to a String.
     * @return the String representation of the supplied {@link GetBlockResult}.
     */
    public static String toUnredactedString(GetBlockResult getBlockResult) {
        StringBuilder sb = new StringBuilder();
        sb.append("{");
        if (getBlockResult.getBlock() != null) {
            sb.append("Block: ").append(toUnredactedString(getBlockResult.getBlock())).append(",");
        }

        if (getBlockResult.getProof() != null) {
            sb.append("Proof: ").append(toUnredactedString(getBlockResult.getProof()));
        }

        sb.append("}");
        return sb.toString();
    }

    /**
     * Returns the string representation of a given {@link GetDigestResult}.
     * Adapted from the AWS SDK autogenerated {@code toString()} method, with sensitive values un-redacted.
     *
     * @param getDigestResult the {@link GetDigestResult} to convert to a String.
     * @return the String representation of the supplied {@link GetDigestResult}.
     */
    public static String toUnredactedString(GetDigestResult getDigestResult) {
        StringBuilder sb = new StringBuilder();
        sb.append("{");
        if (getDigestResult.getDigest() != null) {
            sb.append("Digest: ").append(getDigestResult.getDigest()).append(",");
        }

        if (getDigestResult.getDigestTipAddress() != null) {
            sb.append("DigestTipAddress: ").append(toUnredactedString(getDigestResult.getDigestTipAddress()));
        }

        sb.append("}");
        return sb.toString();
    }
}

Verifier.java

2.x


/*
 * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: MIT-0
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package software.amazon.qldb.tutorial;

import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Comparator;
import java.util.Iterator;
import java.util.List;
import java.util.concurrent.ThreadLocalRandom;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.amazonaws.util.Base64;

import software.amazon.qldb.tutorial.qldb.Proof;

/**
 * Encapsulates the logic to verify the integrity of revisions or blocks in a QLDB ledger.
 *
 * The main entry point is {@link #verify(byte[], byte[], String)}.
 *
 * This code expects that you have AWS credentials setup per:
 * http://docs.aws.amazon.com/java-sdk/latest/developer-guide/setup-credentials.html
 */
public final class Verifier {
    public static final Logger log = LoggerFactory.getLogger(Verifier.class);
    private static final int HASH_LENGTH = 32;
    private static final int UPPER_BOUND = 8;

    /**
     * Compares two hashes by their <em>signed</em> byte values in little-endian order.
     */
    private static Comparator<byte[]> hashComparator = (h1, h2) -> {
        if (h1.length != HASH_LENGTH || h2.length != HASH_LENGTH) {
            throw new IllegalArgumentException("Invalid hash.");
        }
        for (int i = h1.length - 1; i >= 0; i--) {
            int byteEqual = Byte.compare(h1[i], h2[i]);
            if (byteEqual != 0) {
                return byteEqual;
            }
        }

        return 0;
    };

    private Verifier() { }

    /**
     * Verify the integrity of a document with respect to a QLDB ledger digest.
     *
     * The verification algorithm includes the following steps:
     *
     * 1. {@link #buildCandidateDigest(Proof, byte[])} build the candidate digest from the internal hashes
     * in the {@link Proof}.
     * 2. Check that the {@code candidateLedgerDigest} is equal to the {@code ledgerDigest}.
     *
     * @param documentHash
     *              The hash of the document to be verified.
     * @param digest
     *              The QLDB ledger digest. This digest should have been retrieved using
     *              {@link com.amazonaws.services.qldb.AmazonQLDB#getDigest}
     * @param proofBlob
     *              The ion encoded bytes representing the {@link Proof} associated with the supplied
     *              {@code digestTipAddress} and {@code address} retrieved using
     *              {@link com.amazonaws.services.qldb.AmazonQLDB#getRevision}.
     * @return {@code true} if the record is verified or {@code false} if it is not verified.
     */
    public static boolean verify(
            final byte[] documentHash,
            final byte[] digest,
            final String proofBlob
    ) {
        Proof proof = Proof.fromBlob(proofBlob);

        byte[] candidateDigest = buildCandidateDigest(proof, documentHash);

        return Arrays.equals(digest, candidateDigest);
    }

    /**
     * Build the candidate digest representing the entire ledger from the internal hashes of the {@link Proof}.
     *
     * @param proof
     *              A Java representation of {@link Proof}
     *              returned from {@link com.amazonaws.services.qldb.AmazonQLDB#getRevision}.
     * @param leafHash
     *              Leaf hash to build the candidate digest with.
     * @return a byte array of the candidate digest.
     */
    private static byte[] buildCandidateDigest(final Proof proof, final byte[] leafHash) {
        return calculateRootHashFromInternalHashes(proof.getInternalHashes(), leafHash);
    }

    /**
     * Get a new instance of {@link MessageDigest} using the SHA-256 algorithm.
     *
     * @return an instance of {@link MessageDigest}.
     * @throws IllegalStateException if the algorithm is not available on the current JVM.
     */
    static MessageDigest newMessageDigest() {
        try {
            return MessageDigest.getInstance("SHA-256");
        } catch (NoSuchAlgorithmException e) {
            log.error("Failed to create SHA-256 MessageDigest", e);
            throw new IllegalStateException("SHA-256 message digest is unavailable", e);
        }
    }

    /**
     * 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 == 0) {
            return h2;
        }
        if (h2.length == 0) {
            return h1;
        }
        byte[] concatenated = new byte[h1.length + h2.length];
        if (hashComparator.compare(h1, h2) < 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 = newMessageDigest();
        messageDigest.update(concatenated);

        return messageDigest.digest();
    }

    /**
     * Starting with the provided {@code leafHash} combined with the provided {@code internalHashes}
     * pairwise until only the root hash remains.
     *
     * @param internalHashes
     *              Internal hashes of Merkle tree.
     * @param leafHash
     *              Leaf hashes of Merkle tree.
     * @return the root hash.
     */
    private static byte[] calculateRootHashFromInternalHashes(final List<byte[]> internalHashes, final byte[] leafHash) {
        return internalHashes.stream().reduce(leafHash, Verifier::dot);
    }

    /**
     * Flip a single random bit in the given byte array. This method is used to demonstrate
     * QLDB's verification features.
     *
     * @param original
     *              The original byte array.
     * @return the altered byte array with a single random bit changed.
     */
    public static byte[] flipRandomBit(final byte[] original) {
        if (original.length == 0) {
            throw new IllegalArgumentException("Array cannot be empty!");
        }
        int alteredPosition = ThreadLocalRandom.current().nextInt(original.length);
        int b = ThreadLocalRandom.current().nextInt(UPPER_BOUND);
        byte[] altered = new byte[original.length];
        System.arraycopy(original, 0, altered, 0, original.length);
        altered[alteredPosition] = (byte) (altered[alteredPosition] ^ (1 << b));
        return altered;
    }

    public static String toBase64(byte[] arr) {
        return new String(Base64.encode(arr), StandardCharsets.UTF_8);
    }

    /**
     * Convert a {@link ByteBuffer} into byte array.
     *
     * @param buffer
     *              The {@link ByteBuffer} to convert.
     * @return the converted byte array.
     */
    public static byte[] convertByteBufferToByteArray(final ByteBuffer buffer) {
        byte[] arr = new byte[buffer.remaining()];
        buffer.get(arr);
        return arr;
    }

    /**
     * Calculates the root hash from a list of hashes that represent the base of a Merkle tree.
     *
     * @param hashes
     *              The list of byte arrays representing hashes making up base of a Merkle tree.
     * @return a byte array that is the root hash of the given list of hashes.
     */
    public static byte[] calculateMerkleTreeRootHash(List<byte[]> hashes) {
        if (hashes.isEmpty()) {
            return new byte[0];
        }

        List<byte[]> remaining = combineLeafHashes(hashes);
        while (remaining.size() > 1) {
            remaining = combineLeafHashes(remaining);
        }
        return remaining.get(0);
    }

    private static List<byte[]> combineLeafHashes(List<byte[]> hashes) {
        List<byte[]> combinedHashes = new ArrayList<>();
        Iterator<byte[]> it = hashes.stream().iterator();

        while (it.hasNext()) {
            byte[] left = it.next();
            if (it.hasNext()) {
                byte[] right = it.next();
                byte[] combined = dot(left, right);
                combinedHashes.add(combined);
            } else {
                combinedHashes.add(left);
            }
        }

        return combinedHashes;
    }
}

1.x


/*
 * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: MIT-0
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package software.amazon.qldb.tutorial;

import com.amazonaws.util.Base64;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import software.amazon.qldb.tutorial.qldb.Proof;

import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.*;
import java.util.concurrent.ThreadLocalRandom;

/**
 * Encapsulates the logic to verify the integrity of revisions or blocks in a QLDB ledger.
 *
 * The main entry point is {@link #verify(byte[], byte[], String)}.
 *
 * This code expects that you have AWS credentials setup per:
 * http://docs.aws.amazon.com/java-sdk/latest/developer-guide/setup-credentials.html
 */
public final class Verifier {
    public static final Logger log = LoggerFactory.getLogger(Verifier.class);
    private static final int HASH_LENGTH = 32;
    private static final int UPPER_BOUND = 8;

    /**
     * Compares two hashes by their <em>signed</em> byte values in little-endian order.
     */
    private static Comparator<byte[]> hashComparator = (h1, h2) -> {
        if (h1.length != HASH_LENGTH || h2.length != HASH_LENGTH) {
            throw new IllegalArgumentException("Invalid hash.");
        }
        for (int i = h1.length - 1; i >= 0; i--) {
            int byteEqual = Byte.compare(h1[i], h2[i]);
            if (byteEqual != 0) {
                return byteEqual;
            }
        }

        return 0;
    };

    private Verifier() { }

    /**
     * Verify the integrity of a document with respect to a QLDB ledger digest.
     *
     * The verification algorithm includes the following steps:
     *
     * 1. {@link #buildCandidateDigest(Proof, byte[])} build the candidate digest from the internal hashes
     * in the {@link Proof}.
     * 2. Check that the {@code candidateLedgerDigest} is equal to the {@code ledgerDigest}.
     *
     * @param documentHash
     *              The hash of the document to be verified.
     * @param digest
     *              The QLDB ledger digest. This digest should have been retrieved using
     *              {@link com.amazonaws.services.qldb.AmazonQLDB#getDigest}
     * @param proofBlob
     *              The ion encoded bytes representing the {@link Proof} associated with the supplied
     *              {@code digestTipAddress} and {@code address} retrieved using
     *              {@link com.amazonaws.services.qldb.AmazonQLDB#getRevision}.
     * @return {@code true} if the record is verified or {@code false} if it is not verified.
     */
    public static boolean verify(
            final byte[] documentHash,
            final byte[] digest,
            final String proofBlob
    ) {
        Proof proof = Proof.fromBlob(proofBlob);

        byte[] candidateDigest = buildCandidateDigest(proof, documentHash);

        return Arrays.equals(digest, candidateDigest);
    }

    /**
     * Build the candidate digest representing the entire ledger from the internal hashes of the {@link Proof}.
     *
     * @param proof
     *              A Java representation of {@link Proof}
     *              returned from {@link com.amazonaws.services.qldb.AmazonQLDB#getRevision}.
     * @param leafHash
     *              Leaf hash to build the candidate digest with.
     * @return a byte array of the candidate digest.
     */
    private static byte[] buildCandidateDigest(final Proof proof, final byte[] leafHash) {
        return calculateRootHashFromInternalHashes(proof.getInternalHashes(), leafHash);
    }

    /**
     * Get a new instance of {@link MessageDigest} using the SHA-256 algorithm.
     *
     * @return an instance of {@link MessageDigest}.
     * @throws IllegalStateException if the algorithm is not available on the current JVM.
     */
    static MessageDigest newMessageDigest() {
        try {
            return MessageDigest.getInstance("SHA-256");
        } catch (NoSuchAlgorithmException e) {
            log.error("Failed to create SHA-256 MessageDigest", e);
            throw new IllegalStateException("SHA-256 message digest is unavailable", e);
        }
    }

    /**
     * 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 == 0) {
            return h2;
        }
        if (h2.length == 0) {
            return h1;
        }
        byte[] concatenated = new byte[h1.length + h2.length];
        if (hashComparator.compare(h1, h2) < 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 = newMessageDigest();
        messageDigest.update(concatenated);

        return messageDigest.digest();
    }

    /**
     * Starting with the provided {@code leafHash} combined with the provided {@code internalHashes}
     * pairwise until only the root hash remains.
     *
     * @param internalHashes
     *              Internal hashes of Merkle tree.
     * @param leafHash
     *              Leaf hashes of Merkle tree.
     * @return the root hash.
     */
    private static byte[] calculateRootHashFromInternalHashes(final List<byte[]> internalHashes, final byte[] leafHash) {
        return internalHashes.stream().reduce(leafHash, Verifier::dot);
    }

    /**
     * Flip a single random bit in the given byte array. This method is used to demonstrate
     * QLDB's verification features.
     *
     * @param original
     *              The original byte array.
     * @return the altered byte array with a single random bit changed.
     */
    public static byte[] flipRandomBit(final byte[] original) {
        if (original.length == 0) {
            throw new IllegalArgumentException("Array cannot be empty!");
        }
        int alteredPosition = ThreadLocalRandom.current().nextInt(original.length);
        int b = ThreadLocalRandom.current().nextInt(UPPER_BOUND);
        byte[] altered = new byte[original.length];
        System.arraycopy(original, 0, altered, 0, original.length);
        altered[alteredPosition] = (byte) (altered[alteredPosition] ^ (1 << b));
        return altered;
    }

    public static String toBase64(byte[] arr) {
        return new String(Base64.encode(arr), StandardCharsets.UTF_8);
    }

    /**
     * Convert a {@link ByteBuffer} into byte array.
     *
     * @param buffer
     *              The {@link ByteBuffer} to convert.
     * @return the converted byte array.
     */
    public static byte[] convertByteBufferToByteArray(final ByteBuffer buffer) {
        byte[] arr = new byte[buffer.remaining()];
        buffer.get(arr);
        return arr;
    }

    /**
     * Calculates the root hash from a list of hashes that represent the base of a Merkle tree.
     *
     * @param hashes
     *              The list of byte arrays representing hashes making up base of a Merkle tree.
     * @return a byte array that is the root hash of the given list of hashes.
     */
    public static byte[] calculateMerkleTreeRootHash(List<byte[]> hashes) {
        if (hashes.isEmpty()) {
            return new byte[0];
        }

        List<byte[]> remaining = combineLeafHashes(hashes);
        while (remaining.size() > 1) {
            remaining = combineLeafHashes(remaining);
        }
        return remaining.get(0);
    }

    private static List<byte[]> combineLeafHashes(List<byte[]> hashes) {
        List<byte[]> combinedHashes = new ArrayList<>();
        Iterator<byte[]> it = hashes.stream().iterator();

        while (it.hasNext()) {
            byte[] left = it.next();
            if (it.hasNext()) {
                byte[] right = it.next();
                byte[] combined = dot(left, right);
                combinedHashes.add(combined);
            } else {
                combinedHashes.add(left);
            }
        }

        return combinedHashes;
    }
}

使用两个.java文件（GetDigest.java和GetRevision.java）执行以下步骤：

从vehicle-registration分类账中请求新摘要。
请索取 VehicleRegistration 表格中每份文件修订版的证明。
通过重新计算摘要，使用返回的摘要和证明验证修订版。

GetDigest.java 程序包含以下代码。


/*
 * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: MIT-0
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package software.amazon.qldb.tutorial;

import com.amazonaws.services.qldb.AmazonQLDB;
import com.amazonaws.services.qldb.model.GetDigestRequest;
import com.amazonaws.services.qldb.model.GetDigestResult;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import software.amazon.qldb.tutorial.qldb.QldbStringUtils;

/**
 * This is an example for retrieving the digest of a particular ledger.
 *
 * This code expects that you have AWS credentials setup per:
 * http://docs.aws.amazon.com/java-sdk/latest/developer-guide/setup-credentials.html
 */
public final class GetDigest {
    public static final Logger log = LoggerFactory.getLogger(GetDigest.class);
    public static AmazonQLDB client = CreateLedger.getClient();

    private GetDigest() { }

    /**
     * Calls {@link #getDigest(String)} for a ledger.
     *
     * @param args
     *              Arbitrary command-line arguments.
     * @throws Exception if failed to get a ledger digest.
     */
    public static void main(final String... args) throws Exception {
        try {

            getDigest(Constants.LEDGER_NAME);

        } catch (Exception e) {
            log.error("Unable to get a ledger digest!", e);
            throw e;
        }
    }

    /**
     * Get the digest for the specified ledger.
     *
     * @param ledgerName
     *              The ledger to get digest from.
     * @return {@link GetDigestResult}.
     */
    public static GetDigestResult getDigest(final String ledgerName) {
        log.info("Let's get the current digest of the ledger named {}.", ledgerName);
        GetDigestRequest request = new GetDigestRequest()
                .withName(ledgerName);
        GetDigestResult result = client.getDigest(request);
        log.info("Success. LedgerDigest: {}.", QldbStringUtils.toUnredactedString(result));
        return result;
    }
}

注意

使用该 getDigest 方法请求一份涵盖分类账中日记账当前提示的摘要。日志提示是指截至QLDB收到您的请求时最近提交的区块。

GetRevision.java 文件包含以下代码。

2.x


/*
 * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: MIT-0
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package software.amazon.qldb.tutorial;

import com.amazon.ion.IonReader;
import com.amazon.ion.IonStruct;
import com.amazon.ion.IonSystem;
import com.amazon.ion.IonValue;
import com.amazon.ion.IonWriter;
import com.amazon.ion.system.IonReaderBuilder;
import com.amazon.ion.system.IonSystemBuilder;
import com.amazonaws.services.qldb.AmazonQLDB;
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.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import software.amazon.qldb.QldbDriver;
import software.amazon.qldb.Result;
import software.amazon.qldb.TransactionExecutor;
import software.amazon.qldb.tutorial.model.SampleData;
import software.amazon.qldb.tutorial.qldb.BlockAddress;
import software.amazon.qldb.tutorial.qldb.QldbRevision;
import software.amazon.qldb.tutorial.qldb.QldbStringUtils;

/**
 * Verify the integrity of a document revision in a QLDB ledger.
 *
 * This code expects that you have AWS credentials setup per:
 * http://docs.aws.amazon.com/java-sdk/latest/developer-guide/setup-credentials.html
 */
public final class GetRevision {
    public static final Logger log = LoggerFactory.getLogger(GetRevision.class);
    public static AmazonQLDB client = CreateLedger.getClient();
    private static final IonSystem SYSTEM = IonSystemBuilder.standard().build();

    private GetRevision() { }

    public static void main(String... args) throws Exception {

        final String vin = SampleData.REGISTRATIONS.get(0).getVin();


        verifyRegistration(ConnectToLedger.getDriver(), Constants.LEDGER_NAME, vin);
    }

    /**
     * Verify each version of the registration for the given VIN.
     *
     * @param driver
     *              A QLDB driver.
     * @param ledgerName
     *              The ledger to get digest from.
     * @param vin
     *              VIN to query the revision history of a specific registration with.
     * @throws Exception if failed to verify digests.
     * @throws AssertionError if document revision verification failed.
     */
    public static void verifyRegistration(final QldbDriver driver, final String ledgerName, final String vin)
            throws Exception {
        log.info(String.format("Let's verify the registration with VIN=%s, in ledger=%s.", vin, ledgerName));

        try {
            log.info("First, let's get a digest.");
            GetDigestResult digestResult = GetDigest.getDigest(ledgerName);

            ValueHolder digestTipAddress = digestResult.getDigestTipAddress();
            byte[] digestBytes = Verifier.convertByteBufferToByteArray(digestResult.getDigest());

            log.info("Got a ledger digest. Digest end address={}, digest={}.",
                QldbStringUtils.toUnredactedString(digestTipAddress),
                Verifier.toBase64(digestBytes));

            log.info(String.format("Next, let's query the registration with VIN=%s. "
                    + "Then we can verify each version of the registration.", vin));
            List<IonStruct> documentsWithMetadataList = new ArrayList<>();
            driver.execute(txn -> {
                documentsWithMetadataList.addAll(queryRegistrationsByVin(txn, vin));
            });
            log.info("Registrations queried successfully!");

            log.info(String.format("Found %s revisions of the registration with VIN=%s.",
                    documentsWithMetadataList.size(), vin));

            for (IonStruct ionStruct : documentsWithMetadataList) {

                QldbRevision document = QldbRevision.fromIon(ionStruct);
                log.info(String.format("Let's verify the document: %s", document));

                log.info("Let's get a proof for the document.");
                GetRevisionResult proofResult = getRevision(
                        ledgerName,
                        document.getMetadata().getId(),
                        digestTipAddress,
                        document.getBlockAddress()
                );

                final IonValue proof = Constants.MAPPER.writeValueAsIonValue(proofResult.getProof());
                final IonReader reader = IonReaderBuilder.standard().build(proof);
                reader.next();
                ByteArrayOutputStream baos = new ByteArrayOutputStream();
                IonWriter writer = SYSTEM.newBinaryWriter(baos);
                writer.writeValue(reader);
                writer.close();
                baos.flush();
                baos.close();
                byte[] byteProof = baos.toByteArray();

                log.info(String.format("Got back a proof: %s", Verifier.toBase64(byteProof)));

                boolean verified = Verifier.verify(
                        document.getHash(),
                        digestBytes,
                        proofResult.getProof().getIonText()
                );

                if (!verified) {
                    throw new AssertionError("Document revision is not verified!");
                } else {
                    log.info("Success! The document is verified");
                }

                byte[] alteredDigest = Verifier.flipRandomBit(digestBytes);
                log.info(String.format("Flipping one bit in the digest and assert that the document is NOT verified. "
                        + "The altered digest is: %s", Verifier.toBase64(alteredDigest)));
                verified = Verifier.verify(
                        document.getHash(),
                        alteredDigest,
                        proofResult.getProof().getIonText()
                );

                if (verified) {
                    throw new AssertionError("Expected document to not be verified against altered digest.");
                } else {
                    log.info("Success! As expected flipping a bit in the digest causes verification to fail.");
                }

                byte[] alteredDocumentHash = Verifier.flipRandomBit(document.getHash());
                log.info(String.format("Flipping one bit in the document's hash and assert that it is NOT verified. "
                        + "The altered document hash is: %s.", Verifier.toBase64(alteredDocumentHash)));
                verified = Verifier.verify(
                        alteredDocumentHash,
                        digestBytes,
                        proofResult.getProof().getIonText()
                );

                if (verified) {
                    throw new AssertionError("Expected altered document hash to not be verified against digest.");
                } else {
                    log.info("Success! As expected flipping a bit in the document hash causes verification to fail.");
                }
            }

        } catch (Exception e) {
            log.error("Failed to verify digests.", e);
            throw e;
        }

        log.info(String.format("Finished verifying the registration with VIN=%s in ledger=%s.", vin, ledgerName));
    }

    /**
     * Get the revision of a particular document specified by the given document ID and block address.
     *
     * @param ledgerName
     *              Name of the ledger containing the document.
     * @param documentId
     *              Unique ID for the document to be verified, contained in the committed view of the document.
     * @param digestTipAddress
     *              The latest block location covered by the digest.
     * @param blockAddress
     *              The location of the block to request.
     * @return the requested revision.
     */
    public static GetRevisionResult getRevision(final String ledgerName, final String documentId,
                                                final ValueHolder digestTipAddress, final BlockAddress blockAddress) {
        try {
            GetRevisionRequest request = new GetRevisionRequest()
                    .withName(ledgerName)
                    .withDigestTipAddress(digestTipAddress)
                    .withBlockAddress(new ValueHolder().withIonText(Constants.MAPPER.writeValueAsIonValue(blockAddress)
                            .toString()))
                    .withDocumentId(documentId);
            return client.getRevision(request);
        } catch (IOException ioe) {
            throw new IllegalStateException(ioe);
        }
    }

    /**
     * Query the registration history for the given VIN.
     *
     * @param txn
     *              The {@link TransactionExecutor} for lambda execute.
     * @param vin
     *              The unique VIN to query.
     * @return a list of {@link IonStruct} representing the registration history.
     * @throws IllegalStateException if failed to convert parameters into {@link IonValue}
     */
    public static List<IonStruct> queryRegistrationsByVin(final TransactionExecutor txn, final String vin) {
        log.info(String.format("Let's query the 'VehicleRegistration' table for VIN: %s...", vin));
        log.info("Let's query the 'VehicleRegistration' table for VIN: {}...", vin);
        final String query = String.format("SELECT * FROM _ql_committed_%s WHERE data.VIN = ?",
                Constants.VEHICLE_REGISTRATION_TABLE_NAME);
        try {
            final List<IonValue> parameters = Collections.singletonList(Constants.MAPPER.writeValueAsIonValue(vin));
            final Result result = txn.execute(query, parameters);
            List<IonStruct> list = ScanTable.toIonStructs(result);
            log.info(String.format("Found %d document(s)!", list.size()));
            return list;
        } catch (IOException ioe) {
            throw new IllegalStateException(ioe);
        }
    }
}

1.x


/*
 * Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
 * SPDX-License-Identifier: MIT-0
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this
 * software and associated documentation files (the "Software"), to deal in the Software
 * without restriction, including without limitation the rights to use, copy, modify,
 * merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
 * permit persons to whom the Software is furnished to do so.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
 * INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
 * PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
 * OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */

package software.amazon.qldb.tutorial;

import com.amazon.ion.IonReader;
import com.amazon.ion.IonStruct;
import com.amazon.ion.IonValue;
import com.amazon.ion.IonWriter;
import com.amazon.ion.system.IonReaderBuilder;
import com.amazonaws.services.qldb.AmazonQLDB;
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 org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import software.amazon.qldb.QldbSession;
import software.amazon.qldb.Result;
import software.amazon.qldb.TransactionExecutor;
import software.amazon.qldb.tutorial.model.SampleData;
import software.amazon.qldb.tutorial.qldb.BlockAddress;
import software.amazon.qldb.tutorial.qldb.QldbRevision;
import software.amazon.qldb.tutorial.qldb.QldbStringUtils;

import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

/**
 * Verify the integrity of a document revision in a QLDB ledger.
 *
 * This code expects that you have AWS credentials setup per:
 * http://docs.aws.amazon.com/java-sdk/latest/developer-guide/setup-credentials.html
 */
public final class GetRevision {
    public static final Logger log = LoggerFactory.getLogger(GetRevision.class);
    public static AmazonQLDB client = CreateLedger.getClient();

    private GetRevision() { }

    public static void main(String... args) throws Exception {

        final String vin = SampleData.REGISTRATIONS.get(0).getVin();

        try (QldbSession qldbSession = ConnectToLedger.createQldbSession()) {
            verifyRegistration(qldbSession, Constants.LEDGER_NAME, vin);
        }
    }

    /**
     * Verify each version of the registration for the given VIN.
     *
     * @param qldbSession
     *              A QLDB session.
     * @param ledgerName
     *              The ledger to get digest from.
     * @param vin
     *              VIN to query the revision history of a specific registration with.
     * @throws Exception if failed to verify digests.
     * @throws AssertionError if document revision verification failed.
     */
    public static void verifyRegistration(final QldbSession qldbSession, final String ledgerName, final String vin)
            throws Exception {
        log.info(String.format("Let's verify the registration with VIN=%s, in ledger=%s.", vin, ledgerName));

        try {
            log.info("First, let's get a digest.");
            GetDigestResult digestResult = GetDigest.getDigest(ledgerName);

            ValueHolder digestTipAddress = digestResult.getDigestTipAddress();
            byte[] digestBytes = Verifier.convertByteBufferToByteArray(digestResult.getDigest());

            log.info("Got a ledger digest. Digest end address={}, digest={}.",
                QldbStringUtils.toUnredactedString(digestTipAddress),
                Verifier.toBase64(digestBytes));

            log.info(String.format("Next, let's query the registration with VIN=%s. "
                    + "Then we can verify each version of the registration.", vin));
            List<IonStruct> documentsWithMetadataList = new ArrayList<>();
            qldbSession.execute(txn -> {
                documentsWithMetadataList.addAll(queryRegistrationsByVin(txn, vin));
            }, (retryAttempt) -> log.info("Retrying due to OCC conflict..."));
            log.info("Registrations queried successfully!");

            log.info(String.format("Found %s revisions of the registration with VIN=%s.",
                    documentsWithMetadataList.size(), vin));

            for (IonStruct ionStruct : documentsWithMetadataList) {

                QldbRevision document = QldbRevision.fromIon(ionStruct);
                log.info(String.format("Let's verify the document: %s", document));

                log.info("Let's get a proof for the document.");
                GetRevisionResult proofResult = getRevision(
                        ledgerName,
                        document.getMetadata().getId(),
                        digestTipAddress,
                        document.getBlockAddress()
                );

                final IonValue proof = Constants.MAPPER.writeValueAsIonValue(proofResult.getProof());
                final IonReader reader = IonReaderBuilder.standard().build(proof);
                reader.next();
                ByteArrayOutputStream baos = new ByteArrayOutputStream();
                IonWriter writer = Constants.SYSTEM.newBinaryWriter(baos);
                writer.writeValue(reader);
                writer.close();
                baos.flush();
                baos.close();
                byte[] byteProof = baos.toByteArray();

                log.info(String.format("Got back a proof: %s", Verifier.toBase64(byteProof)));

                boolean verified = Verifier.verify(
                        document.getHash(),
                        digestBytes,
                        proofResult.getProof().getIonText()
                );

                if (!verified) {
                    throw new AssertionError("Document revision is not verified!");
                } else {
                    log.info("Success! The document is verified");
                }

                byte[] alteredDigest = Verifier.flipRandomBit(digestBytes);
                log.info(String.format("Flipping one bit in the digest and assert that the document is NOT verified. "
                        + "The altered digest is: %s", Verifier.toBase64(alteredDigest)));
                verified = Verifier.verify(
                        document.getHash(),
                        alteredDigest,
                        proofResult.getProof().getIonText()
                );

                if (verified) {
                    throw new AssertionError("Expected document to not be verified against altered digest.");
                } else {
                    log.info("Success! As expected flipping a bit in the digest causes verification to fail.");
                }

                byte[] alteredDocumentHash = Verifier.flipRandomBit(document.getHash());
                log.info(String.format("Flipping one bit in the document's hash and assert that it is NOT verified. "
                        + "The altered document hash is: %s.", Verifier.toBase64(alteredDocumentHash)));
                verified = Verifier.verify(
                        alteredDocumentHash,
                        digestBytes,
                        proofResult.getProof().getIonText()
                );

                if (verified) {
                    throw new AssertionError("Expected altered document hash to not be verified against digest.");
                } else {
                    log.info("Success! As expected flipping a bit in the document hash causes verification to fail.");
                }
            }

        } catch (Exception e) {
            log.error("Failed to verify digests.", e);
            throw e;
        }

        log.info(String.format("Finished verifying the registration with VIN=%s in ledger=%s.", vin, ledgerName));
    }

    /**
     * Get the revision of a particular document specified by the given document ID and block address.
     *
     * @param ledgerName
     *              Name of the ledger containing the document.
     * @param documentId
     *              Unique ID for the document to be verified, contained in the committed view of the document.
     * @param digestTipAddress
     *              The latest block location covered by the digest.
     * @param blockAddress
     *              The location of the block to request.
     * @return the requested revision.
     */
    public static GetRevisionResult getRevision(final String ledgerName, final String documentId,
                                                final ValueHolder digestTipAddress, final BlockAddress blockAddress) {
        try {
            GetRevisionRequest request = new GetRevisionRequest()
                    .withName(ledgerName)
                    .withDigestTipAddress(digestTipAddress)
                    .withBlockAddress(new ValueHolder().withIonText(Constants.MAPPER.writeValueAsIonValue(blockAddress)
                            .toString()))
                    .withDocumentId(documentId);
            return client.getRevision(request);
        } catch (IOException ioe) {
            throw new IllegalStateException(ioe);
        }
    }

    /**
     * Query the registration history for the given VIN.
     *
     * @param txn
     *              The {@link TransactionExecutor} for lambda execute.
     * @param vin
     *              The unique VIN to query.
     * @return a list of {@link IonStruct} representing the registration history.
     * @throws IllegalStateException if failed to convert parameters into {@link IonValue}
     */
    public static List<IonStruct> queryRegistrationsByVin(final TransactionExecutor txn, final String vin) {
        log.info(String.format("Let's query the 'VehicleRegistration' table for VIN: %s...", vin));
        log.info("Let's query the 'VehicleRegistration' table for VIN: {}...", vin);
        final String query = String.format("SELECT * FROM _ql_committed_%s WHERE data.VIN = ?",
                Constants.VEHICLE_REGISTRATION_TABLE_NAME);
        try {
            final List<IonValue> parameters = Collections.singletonList(Constants.MAPPER.writeValueAsIonValue(vin));
            final Result result = txn.execute(query, parameters);
            List<IonStruct> list = ScanTable.toIonStructs(result);
            log.info(String.format("Found %d document(s)!", list.size()));
            return list;
        } catch (IOException ioe) {
            throw new IllegalStateException(ioe);
        }
    }
}

注意

在该getRevision方法返回指定文档修订版本的证明后，此程序使用客户端API来验证该修订版。有关其使用的算法的概述API，请参阅使用证明重新计算您的摘要。

编译并运行GetRevision.java程序以加密方式验证VehicleRegistrationVIN1N4AL11D75C109151文档。

要导出和验证 vehicle-registration 分类账中的日记账数据，请继续步骤 8：导出并验证分类账中的日记账数据。

Javascript 在您的浏览器中被禁用或不可用。

要使用 Amazon Web Services 文档，必须启用 Javascript。请参阅浏览器的帮助页面以了解相关说明。

文档惯例

查看开发工具包的修订历史记录

步骤 8：导出和验证日记账数据