B4X Requires Chilkat v11.0.0+

Verify an RSA Signature Against the Signed Hash

See more Apple Keychain Examples

Demonstrates how to validate an RSA Signature against the hash that was signed. B4X

Dim success As Boolean = False

Dim bd As ChilkatBinData
bd.Initialize
Dim i As Int
For i = 0 To 100
    bd.AppendEncoded("000102030405060708090A0B0C0D0E0F", "hex")
Next
Dim sha256_base64 As String = bd.GetHash("sha256", "base64")
Log("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 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 hash against the signature.
rsa.EncodingMode = "base64"
success = rsa.VerifyHashENC(sha256_base64, "sha256", base64_rsa_sig)

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