RSA SignatureException：签名长度不正确

问题描述

我在签名rsa签名时遇到问题。我有一个已用私钥加密的签名。但是，当尝试使用公钥验证它时出现问题。我收到以下异常：

I am having issues signing an rsa signature. I have a signature that has been encrypted with a private key. I have an issue when trying to validate it with the public key however. I get the following exception:

java.security.SignatureException: Signature length not correct: got 336 but was expecting 128
    at sun.security.rsa.RSASignature.engineVerify(RSASignature.java:189)
    at java.security.Signature$Delegate.engineVerify(Signature.java:1219)
    at java.security.Signature.verify(Signature.java:652)
    at XmlReader.main(XmlReader.java:65)

我已经通过以下方式检索了我的签名和公钥：

I have retrieved my signature and public key the following way:

    BigInteger modulus = new BigInteger(Base64.getDecoder().decode(publicKeyString));
    BigInteger exponent = new BigInteger(Base64.getDecoder().decode("AQAB"));

    RSAPublicKeySpec keySpec = new RSAPublicKeySpec(modulus, exponent);
    KeyFactory keyFactory = KeyFactory.getInstance("RSA");
    PublicKey pubKey = keyFactory.generatePublic(keySpec);

    byte[] sigToVerify = Base64.getDecoder().decode(signatureString);
    Signature sig = Signature.getInstance("MD5WithRSA");
    sig.initVerify(pubKey);
    boolean verifies = sig.verify(sigToVerify);

应用程序在最后一行失败。对导致异常的原因有何想法？

The application fails at the last line. Any thoughts as to where this exception is caused?

更新：

已添加要验证签名的数据：

Added data for signature to be verified:

        String data = "...." //hidden since sensitive data
        byte[] dataBytes = Base64.getEncoder().encode(data.getBytes());
        dataBytes = Base64.getDecoder().decode(dataBytes);

推荐答案

在调用 sig.verify之前（sigToVerify）您应该致电

sig.update(data);

传递您要验证签名的数据。

passing the data you're verifying signature for.

并确保在参数中调用 verify 仅具有签名字节。

And make sure that calling verify in your argument you have signature bytes only.

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