CODEWITHSUNDEEP
javagodsa
TBC
TBC

Reputation: 43

Difference between Go DSA and Java DSA

  1. Go generates a signature using a DSA private key
  2. Java verifies first step result using the DSA public key
  3. Java should return true, but returns false
package main
import (
    "crypto/dsa"
    "crypto/rand"
    "encoding/asn1"
    "encoding/hex"
    "fmt"
    "golang.org/x/crypto/ssh"
    "math/big"
)

func main() {
    // a dsa private key
    pemData := []byte("-----BEGIN DSA PRIVATE KEY-----\n" +
        "MIIBvAIBAAKBgQD9f1OBHXUSKVLfSpwu7OTn9hG3UjzvRADDHj+AtlEmaUVdQCJR\n" +
        "+1k9jVj6v8X1ujD2y5tVbNeBO4AdNG/yZmC3a5lQpaSfn+gEexAiwk+7qdf+t8Yb\n" +
        "+DtX58aophUPBPuD9tPFHsMCNVQTWhaRMvZ1864rYdcq7/IiAxmd0UgBxwIVAJdg\n" +
        "UI8VIwvMspK5gqLrhAvwWBz1AoGBAPfhoIXWmz3ey7yrXDa4V7l5lK+7+jrqgvlX\n" +
        "TAs9B4JnUVlXjrrUWU/mcQcQgYC0SRZxI+hMKBYTt88JMozIpuE8FnqLVHyNKOCj\n" +
        "rh4rs6Z1kW6jfwv6ITVi8ftiegEkO8yk8b6oUZCJqIPf4VrlnwaSi2ZegHtVJWQB\n" +
        "TDv+z0kqAoGBAIb9o0KPsjAdzjK571e1Mx7ZhEyJGrcxHiN2sW8IztEbqrKKiMxp\n" +
        "NlTwm234uBdtzVHE3uDWZpfHPMIRmwBjCYDFRowWWVRdhdFXZlpCyp1gMWqJ11dh\n" +
        "3FI3+O43DevRSyyuLRVCNQ1J3iVgwY5ndRpZU7n6y8DPH4/4EBT7KvnVAhR4Vwun\n" +
        "Fhu/+4AGaVeMEa814I3dqg==\n" +
        "-----END DSA PRIVATE KEY-----")
    // parse dsa 
    p, _ := ssh.ParseRawPrivateKey(pemData)
    pp := p.(*dsa.PrivateKey)

    // orign data
    hashed := []byte{1}
    r, s, _ := dsa.Sign(rand.Reader, pp, hashed)

    type dsaSignature struct {
        R, S *big.Int
    }
    var ss dsaSignature
    ss.S = s
    ss.R = r
    signatureBytes, _ := asn1.Marshal(ss)

    // print sign 
    fmt.Println(hex.EncodeToString(signatureBytes))
}
  1. Java reads the DSA public key and initialize a signer
  2. Java verify first step sign result
  3. returns false
@Test
public void ttt() throws InvalidKeySpecException, NoSuchAlgorithmException, InvalidKeyException, SignatureException {
        // DSA public key
        String pubKey = "-----BEGIN PUBLIC KEY-----\n" +
                "MIIBuDCCASwGByqGSM44BAEwggEfAoGBAP1/U4EddRIpUt9KnC7s5Of2EbdSPO9E\n" +
                "AMMeP4C2USZpRV1AIlH7WT2NWPq/xfW6MPbLm1Vs14E7gB00b/JmYLdrmVClpJ+f\n" +
                "6AR7ECLCT7up1/63xhv4O1fnxqimFQ8E+4P208UewwI1VBNaFpEy9nXzrith1yrv\n" +
                "8iIDGZ3RSAHHAhUAl2BQjxUjC8yykrmCouuEC/BYHPUCgYEA9+GghdabPd7LvKtc\n" +
                "NrhXuXmUr7v6OuqC+VdMCz0HgmdRWVeOutRZT+ZxBxCBgLRJFnEj6EwoFhO3zwky\n" +
                "jMim4TwWeotUfI0o4KOuHiuzpnWRbqN/C/ohNWLx+2J6ASQ7zKTxvqhRkImog9/h\n" +
                "WuWfBpKLZl6Ae1UlZAFMO/7PSSoDgYUAAoGBAIb9o0KPsjAdzjK571e1Mx7ZhEyJ\n" +
                "GrcxHiN2sW8IztEbqrKKiMxpNlTwm234uBdtzVHE3uDWZpfHPMIRmwBjCYDFRowW\n" +
                "WVRdhdFXZlpCyp1gMWqJ11dh3FI3+O43DevRSyyuLRVCNQ1J3iVgwY5ndRpZU7n6\n" +
                "y8DPH4/4EBT7KvnV\n" +
                "-----END PUBLIC KEY-----";
        String publicKeyPEM = pubKey
                .replace("-----BEGIN PUBLIC KEY-----\n", "")
                .replaceAll(System.lineSeparator(), "")
                .replace("-----END PUBLIC KEY-----", "");
        byte[] publicEncoded = Base64.decodeBase64(publicKeyPEM);
        KeyFactory keyFactory1 = KeyFactory.getInstance("DSA");
        X509EncodedKeySpec publicKeySpec = new X509EncodedKeySpec(publicEncoded);
        DSAPublicKey pubKeyy = (DSAPublicKey) keyFactory1.generatePublic(publicKeySpec);

        // init signer
        Signature sig1 = Signature.getInstance("DSA");
        sig1.initVerify(pubKeyy);
        sig1.update(new byte[]{1});
        
        // verify first result
        System.out.println(sig1.verify(HexUtil.decodeHex("first step result")));
}
  1. i tred to use NONEwithDSA within the Java implementation but it didnt do it
  2. Signature sig1 = Signature.getInstance("NONEwithDSA");
java.security.SignatureException: Data for RawDSA must be exactly 20 bytes long
  1. i tred to use SHA1withDSA within the Java implementation but it didnt do it
  2. Signature sig1 = Signature.getInstance("SHA1withDSA");
  3. returns false

Upvotes: 1

Views: 316

Answers (1)

dave_thompson_085
dave_thompson_085

Reputation: 38771

In Java the (Signature) algorithm name DSA is an alias for SHA1withDSA, i.e. the original FIPS186-0 algorithm. This is not the same as the nonstandard 'raw' primitive apparently implemented by Go. NONEwithDSA is indeed the correct Java name for what you want, but the implementation in the 'standard' (SUN) provider is something of a kludge that requires exactly 20 bytes of data, not more or less, because that was the size of the SHA1 hash which was the only standard hash for DSA prior to FIPS186-3.

If you (have or can get and) use the BouncyCastle provider, it does not have this restriction, and should work for your code changed to NONEwithDSA (and either the code or security config modified so that BC is selected as the provider, of course).

If you don't use Bouncy, I think you'll have to code the algorithm yourself; I don't think there's any way to get the SUN implementation to do what you want.

Although it would be better to sign a properly-sized hash as specified in the standard, not raw data, and then you could use the Java providers as specified and designed.

Upvotes: 2

Related Questions