B4X Requires Chilkat v11.0.0+

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. B4X

Dim success As Boolean = False

'  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 ChilkatStringBuilder
sb.Initialize
Dim crlfLineEnding As Boolean = True
Dim i As Int
For i = 0 To 10
    sb.AppendLine("This is a test.", crlfLineEnding)
Next

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

'  Get the public key to be used for signature verification.
Dim pubKey As ChilkatPublicKey
pubKey.Initialize
success = pubKey.LoadFromFile("rsaKeys/chilkat-rsa-2048.pem")
If success = False Then
    Log(pubKey.LastErrorText)
    Return
End If


Dim rsa As ChilkatRsa
rsa.Initialize
success = rsa.UsePublicKey(pubKey)
If success = False Then
    Log(rsa.LastErrorText)
    Return
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 = sb.GetAsString
success = rsa.VerifyStringENC(signedString, "sha256", base64_rsa_sig)

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