Visual Basic 6.0

Verify an RSA Signature Against the Signed String

See more Apple Keychain Examples

Demonstrates how to validate an RSA Signature against the string that was signed. Visual Basic 6.0

Dim success As Long
success = 0

' Create the same string we previously signed in this example: 
' RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

Dim sb As New ChilkatStringBuilder
Dim crlfLineEnding As Long
crlfLineEnding = 1
Dim i As Long
For i = 0 To 10
    success = sb.AppendLine("This is a test.",crlfLineEnding)
Next

Dim base64_rsa_sig As String
base64_rsa_sig = "gWgpEXQqvXN6wh0MuFXPiw2xCb8cnmdizBT1TD1Tpm2GlJ8gnD59DGSj35GGXk1tM+mCOvMa2uW/9gmz8p6A90JLbn918i/2wKGvcde4wXnzPO7JADSNn2UwYzf3rp4/q/JrHv1GZETRJhABSFqTxOgdmdbEJQE/zijOSctCtQAM2CTb6t2BO8uHKSSUAwPH2cbeWxqsaVRLT4ruk5nZOxhoLgLMSjupiSzbE8zSTkkFOEHD+Mbb2xwg85AI0E4DsUnp+hLwwtS0blesgSyvtBY8oJODJeFcJsR7JDOTPdzHQHgJRl/2A4ij5xT91TpXy7ok43jhT6O9j7Q3qrafIQ=="

' Get the public key to be used for signature verification.
Dim pubKey As New PublicKey
success = pubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem")
If (success = 0) Then
    Debug.Print pubKey.LastErrorText
    Exit Sub
End If

Dim rsa As New ChilkatRsa
success = rsa.UsePublicKey(pubKey)
If (success = 0) Then
    Debug.Print rsa.LastErrorText
    Exit Sub
End If

' Verify the string against the signature.
' We signed the utf-8 byte representation of the string, so we must indicate
' to also validate against the utf-8 byte representation.
rsa.Charset = "utf-8"
rsa.EncodingMode = "base64"
Dim signedString As String
signedString = sb.GetAsString()
success = rsa.VerifyStringENC(signedString,"sha256",base64_rsa_sig)

If (success = 0) Then
    Debug.Print rsa.LastErrorText
    Debug.Print "Signature invalid."
Else
    Debug.Print "Signature valid."
End If