Bouncy Castle：多个PGPSignature在同一时间范围内相同(~1秒）

Question

import java.io.IOException;
import java.math.BigInteger;
import java.security.SecureRandom;
import java.time.ZonedDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Arrays;
import java.util.Base64;
import java.util.Date;
import java.util.Iterator;

import org.bouncycastle.bcpg.PublicKeyAlgorithmTags;
import org.bouncycastle.crypto.generators.RSAKeyPairGenerator;
import org.bouncycastle.crypto.params.RSAKeyGenerationParameters;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.openpgp.PGPException;
import org.bouncycastle.openpgp.PGPKeyPair;
import org.bouncycastle.openpgp.PGPPrivateKey;
import org.bouncycastle.openpgp.PGPPublicKey;
import org.bouncycastle.openpgp.PGPSignature;
import org.bouncycastle.openpgp.PGPSignatureGenerator;
import org.bouncycastle.openpgp.PGPSignatureSubpacketGenerator;
import org.bouncycastle.openpgp.PGPUtil;
import org.bouncycastle.openpgp.operator.bc.BcPGPKeyPair;
import org.bouncycastle.openpgp.operator.jcajce.JcaPGPContentSignerBuilder;

public class PgpSimpleSigner {

    private static final DateTimeFormatter FMT = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss.SSS" + "SSS" + "SSS");

    public         final PGPPrivateKey     privateKey;
    public         final PGPPublicKey      publicKey;

    private PgpSimpleSigner() throws IOException, PGPException {

        final RSAKeyGenerationParameters kgp = new RSAKeyGenerationParameters(BigInteger.valueOf(0x10001), new SecureRandom(), 2048, 12);
        final RSAKeyPairGenerator        kpg = new RSAKeyPairGenerator();
                                         kpg.init(kgp);

        final PGPKeyPair  keyPair = new BcPGPKeyPair(PGPPublicKey.RSA_SIGN, kpg.generateKeyPair(), new Date());

        this.privateKey = keyPair.getPrivateKey();
        this.publicKey  = keyPair.getPublicKey();
    }

    private PGPSignature sign(final String signMeString) throws Exception {

        final int keyAlgorithm  = PublicKeyAlgorithmTags.RSA_SIGN;
        final int hashAlgorithm = PGPUtil.SHA256;

        final JcaPGPContentSignerBuilder csb = new JcaPGPContentSignerBuilder(keyAlgorithm, hashAlgorithm);
                                         csb.setProvider(new BouncyCastleProvider());

        final PGPSignatureGenerator          sGen  = new PGPSignatureGenerator(csb);
        final PGPSignatureSubpacketGenerator spGen = new PGPSignatureSubpacketGenerator();

        sGen.init(PGPSignature.CANONICAL_TEXT_DOCUMENT, this.privateKey);

        final Iterator<String> it = this.publicKey.getUserIDs();

        if (it.hasNext()) {
            spGen.addSignerUserID(false, it.next());
            sGen .setHashedSubpackets(spGen.generate());
        }

        sGen.update(signMeString.getBytes());

        return sGen.generate();
        /*
         * The above logic based on Method
         * signFile(String, InputStream, OutputStream, char[], String)
         * in
         * org.bouncycastle.openpgp.examples.ClearSignedFileProcessor.
         * 
         * ...but without the complicated CR/LF & Whitespace logic
         * as we know our input String is RFC 4880 compliant.
         */
    }

    public static void main(final String[] args) throws Throwable {

        final PgpSimpleSigner pgpSimpleSigner = new PgpSimpleSigner();

        byte[] bcSigBytesPrev = {};
        long   t0             = System.nanoTime();

        while (true) {
            final long         nsSinceDelta = System.nanoTime() - t0;
            final PGPSignature bcSig        = pgpSimpleSigner.sign("Sign me, I'm RFC 4880 compliant");
            final byte[]       bcSigBytes   = bcSig.getSignature();

            if (Arrays.compare(bcSigBytesPrev,  bcSigBytes) != 0) {
                               bcSigBytesPrev = bcSigBytes;
                
                System.out.println(FMT.format(ZonedDateTime.now()) + "\t" + nsSinceDelta + "\t" + Base64.getEncoder().encodeToString(bcSigBytes));

                t0 = System.nanoTime();
            }
        }
    }
}

Answer 1

检查org.bouncycastle.bcpg.sig.SignatuRecreationTime.TimeTobytes()的源代码，了解日期值如何添加到字节数组中进行签名：

protected static byte[] timeToBytes(
    Date    date)
{
    byte[]    data = new byte[4];
    long        t = date.getTime() / 1000;
    
    data[0] = (byte)(t >> 24);
    data[1] = (byte)(t >> 16);
    data[2] = (byte)(t >> 8);
    data[3] = (byte)t;
    
    return data;
}

如您所见，使用的是最小到秒的当前时间(date.getTime()返回毫秒，/1000“删除”毫秒部分）。

看起来这是符合RFC4880-5.9的。文字数据包（标记11）部分：

 - A four-octet number that indicates a date associated with the
   literal data.  Commonly, the date might be the modification date
   of a file, or the time the packet was created, or a zero that
   indicates no specific time.

所以它看起来像是在按指定的方式工作。