Problem using RSAPKCS1SignatureFormatter

[dhanasekar]

Hi,
I have to generate message digest using SHA1 algorithm to produce 160 bit number. Then message digest is encrypted with signer's private key(using RSA ECB and PKCS#1 v1.5 padding) and convert to printable hex format.

For the above specification i have tried the following code, I am getting Invalid PKCS#1 padding: no leading zero error (java.security.SignatureException, javax.crypto.BadPaddingException:) on the receiver end. They are using Java interface to handle these messages.

Is there any other method to create ECB and PKCS#1 v1.5 padding using .NET ?

Imports System.Security
Imports System.Security.Cryptography
Imports Microsoft.Web.Services.Security
Imports Microsoft.Web.Services.Security.X509

Public Function fnDigitalSign1(ByVal strMessage As String) As String

Dim​

​

rsaCSP As New System.Security.Cryptography.RSACryptoServiceProvider
Dim toEncrypt() As Byte
Dim encrypted() As Byte
Dim digest() As Byte

Dim enc As New UnicodeEncoding
toEncrypt = enc.GetBytes(strMessage)

'compute hash with algorithm specified as here we have SHA1
Dim sha1Algo As New SHA1Managed
digest = sha1Algo.ComputeHash(toEncrypt)

Dim cert As X509Certificate = fnGetCertificate()
'Here i am getting correct certificate only.
If cert.SupportsDigitalSignature() Then
Dim objRSA As RSAPKCS1SignatureFormatter
objRSA = New RSAPKCS1SignatureFormatter(cert.Key)
objRSA.SetHashAlgorithm("SHA1")
encrypted = objRSA.CreateSignature(digest)
End If


Dim strHEX As String = getHEXformat(encrypted)
​

End Function


Private Function fnGetCertificate() As X509Certificate

​

Dim store As X509CertificateStore
store = X509CertificateStore.CurrentUserStore(X509CertificateStore.MyStore)
store.OpenRead()
Dim cert As X509Certificate = store.Certificates(0)
Return cert​

​

​

End Function

Private Function getHEXformat(ByVal encrypted() As Byte) As String

Dim b As Byte
Dim hexString As String
For Each b In encrypted
hexString += String.Format("{0:X2}", b)
Next
Return hexString.ToLower
End Function


'And I am trying with RSACryptoService provider also

Public Function fnDigitalSign2(ByVal strMessage As String) As String
Try

​

Dim cert As X509Certificate = fnGetCertificate()
'Receiver's Public
Dim receiver_public As RSAParameters = cert.Key.ExportParameters(False)
Dim sender_private As RSAParameters = cert.Key.ExportParameters(True)
Dim toEncrypt() As Byte
Dim encrypted() As Byte
Dim cipher() As Byte
Dim digest() As Byte
toEncrypt = fnGetEncodedBytes(strMessage, SelectEncode.ASCII)
'compute hash with algorithm specified as here we have SHA1
digest = fnComputeSHA1Hash(toEncrypt)
Dim rsaCSP As New System.Security.Cryptography.RSACryptoServiceProvider
rsaCSP.ImportParameters(sender_private)
cipher = rsaCSP.Encrypt(digest, False) 'False to create PKCS#1 padding
Return getHEXformat(cipher)
​

Catch ex As Exception
End Try
​

End Function '