带有SHA256的RSACryptoServiceProvider.SignHash返回128个字节而不是32个字节？

Question

I'm new to cryptography, so perhaps I'm confused on what should happen here. I start with a 32 byte message digest and attempt to sign it using my private key. The output of RSA.SignHash is a 128 bytes. I am expecting 32.

    static private byte[] RSAHashAndSignData(byte[] data, RSAParameters privateKey)
    {
        byte[] signedHash;
        //Create a new instance of RSACryptoServiceProvider.
        using (RSACryptoServiceProvider RSA = new RSACryptoServiceProvider())
        {
            //Import the public key 
            RSA.ImportParameters(privateKey);

            //Encrypt the passed byte array
            var sha = SHA256Managed.Create();
            var digest = sha.ComputeHash(data);
            signedHash = RSA.SignHash(digest, HashAlgorithmName.SHA256, RSASignaturePadding.Pkcs1);
        }

        return signedHash;
    }

Answer 1

I am expecting 32.

That is an incorrect assumption. Signing does not produce a size equal to the size of the input.

Using PKCS#1 padding, using a 1024-bit RSA key will produce as 128-byte signature. The size of a signature is related to the size of the modulus of the signing key.