CODEWITHSUNDEEP
.netcryptographydigital-signaturepycryptorsacryptoserviceprovider
Neyton Luiz Dalle Molle
Neyton Luiz Dalle Molle

Reputation: 71

PyCrypto Sign Message and Verify Signature in .NET RSACryptoServiceProvider

I'm trying to create a signature verification system that uses my website which runs on the Google API with PyCrypto Engine. The program that generates signature is quite simple:

from Crypto.PublicKey import RSA
from Crypto.Hash import MD5
def sign(key, message):
   digest = MD5.new(message).digest()
   signature = key.sign( digest, None )[0]
   signature = hex(signature).replace("0x","").replace("L","").upper()
   if len(signature) % 2==1:
      signature = "0" + sig 
   return signature

The key 'key' is provided by:

RSA.construct((m, e, d, p, q))

The signature is returned as a hex string, such as: "A12D......."

.NET program is:

    Private Function Verify(ByVal message As String, ByVal sign As String) As Boolean
    Dim md5 As New MD5CryptoServiceProvider
    Dim f As New StreamReader("D:/KEY.XML")
    Dim xml As String = f.ReadToEnd
    f.Close()

    Dim rsa As New RSACryptoServiceProvider
    rsa.FromXmlString(xml)

    Dim msg_as_bytes As Byte() = Encoding.Default.GetBytes(message)
    Dim hash_as_bytes As Byte() = md5.ComputeHash(msg_as_bytes)

    ''Dim sig_as_bytes As Byte() = convtobytes(sign)

    Dim sig_as_bytes As Byte() = New Byte(sign.Length / 2 - 1) {}
    For i As Integer = 1 To sign.Length / 2
        sig_as_bytes(i - 1) = CByte("&H" & Mid(sign, (i - 1) * 2 + 1, 2))
    Next

    Return rsa.VerifyData(hash_as_bytes, "SHA1", sig_as_bytes)
End Function

But it does not work!!! Why??

Pycrypto and .NET receive the same parameters (modulus, exponent, d, p, q)

Upvotes: 3

Views: 1880

Answers (2)

Neyton Luiz Dalle Molle
Neyton Luiz Dalle Molle

Reputation: 71

I finished!

The solution is to use Crypto.Signature.PKCS1_v1_5

from Crypto.Hash import SHA
from Crypto.PublicKey import RSA
from Crypto.Util import number
from Crypto.Signature import PKCS1_v1_5

m = 123....
e = 1111....
d = 123....
p = 365...
q = 657...

key = RSA.construct((m, e, d, p, q))

message = "message to be signed"

def assina(message):
    h = SHA.new(message)
    signer = PKCS1_v1_5.new(key)
    signature = signer.sign(h)
    return ByteToHex(signature)

And .NET code to verify:

Private Function Verify(ByVal message As String, ByVal sign As String) As Boolean
    Dim rsa As New RSACryptoServiceProvider()
    rsa.FromXmlString(_pubKey)

    Dim msg_as_bytes As Byte() = Encoding.Default.GetBytes(message)

    Dim sig_as_bytes As Byte() = New Byte(CInt(sign.Length / 2) - 1) {}

    For i As Integer = 1 To sign.Length / 2
        sig_as_bytes(i - 1) = CByte("&H" & Mid(sign, (i - 1) * 2 + 1, 2))
    Next

    Return rsa.VerifyData(msg_as_bytes, "SHA", sig_as_bytes)
End Function

Upvotes: 4

poupou
poupou

Reputation: 43543

Look at both lines:

digest = MD5.new(message).digest()

Return rsa.VerifyData(hash_as_bytes, "SHA1", sig_as_bytes)

Even if you're using a MD5CryptoServiceProvider in your .NET code your still asking the verification to use SHA1 and that won't work. Try changing this to MD5.

Upvotes: 1

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