VB.NET

Verify an RSA Signature Against the Signed Hash

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Demonstrates how to validate an RSA Signature against the hash that was signed. VB.NET

Dim success As Boolean = False

Dim bd As New Chilkat.BinData
Dim i As Integer
For i = 0 To 100
    bd.AppendEncoded("000102030405060708090A0B0C0D0E0F","hex")
Next
Dim sha256_base64 As String = bd.GetHash("sha256","base64")
Debug.WriteLine("sha256 hash in base64 format: " & sha256_base64)

Dim base64_rsa_sig As String = "AwF2BbOvL6jA5DwmMAc9n6J2Cc8PI6Rj5W079+aKJcIEtPWRzHor0Bvc3aftGM3Jbgj6SXlIC3M3RYS7UZOnfiHKFNZgbxaNT5WwsWooK42ZkC8DBZl0p7OunBUKd5SciUo+TKilioeUkriN3L1Zl9hwi3HVDVqgVo3XXskwIftSqLSFlepTLTmOWj9Y93dp8J4D9RyLtNgFQBc0WB22tyJTsuY56mLcWe1AMF3LizB9OrbwjynF2u16xWlrJdugccz795fJBUV9aQSD+8S3KeqwQhoi8RK1uhD68aGCyaSpBq0NZ8COAkn7MXaF4POxrAAt8udfHM+PRfSOptcH/w=="

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


Dim rsa As New Chilkat.Rsa
success = rsa.UsePublicKey(pubKey)
If (success = False) Then
    Debug.WriteLine(rsa.LastErrorText)
    Exit Sub
End If


' Verify the hash against the signature.
rsa.EncodingMode = "base64"
success = rsa.VerifyHashENC(sha256_base64,"sha256",base64_rsa_sig)

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