(Classic ASP) 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.

Chilkat ActiveX Downloads

ActiveX for 32-bit and 64-bit Windows

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<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
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<%
' Create the same string we previously signed in this example: 
' RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.StringBuilder")
set sb = Server.CreateObject("Chilkat.StringBuilder")
crlfLineEnding = 1

For i = 0 To 10
    success = sb.AppendLine("This is a test.",crlfLineEnding)
Next

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

' Get the public key to be used for signature verification.
' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.PublicKey")
set pubKey = Server.CreateObject("Chilkat.PublicKey")
success = pubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem")
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( pubKey.LastErrorText) & "</pre>"
    Response.End
End If

' For versions of Chilkat < 10.0.0, use CreateObject("Chilkat_9_5_0.Rsa")
set rsa = Server.CreateObject("Chilkat.Rsa")
success = rsa.ImportPublicKeyObj(pubKey)

' 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"
signedString = sb.GetAsString()
success = rsa.VerifyStringENC(signedString,"sha256",base64_rsa_sig)

If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( rsa.LastErrorText) & "</pre>"
    Response.Write "<pre>" & Server.HTMLEncode( "Signature invalid.") & "</pre>"
Else
    Response.Write "<pre>" & Server.HTMLEncode( "Signature valid.") & "</pre>"
End If


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