(DataFlex) 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.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

Use ChilkatAx-win32.pkg

Procedure Test
    Handle hoBd
    Integer i
    Boolean iSuccess
    String sSha256_base64
    String sBase64_rsa_sig
    Variant vPubKey
    Handle hoPubKey
    Boolean iSuccess
    Handle hoRsa
    String sTemp1

    Get Create (RefClass(cComChilkatBinData)) To hoBd
    If (Not(IsComObjectCreated(hoBd))) Begin
        Send CreateComObject of hoBd
    End

    For i From 0 To 100
        Get ComAppendEncoded Of hoBd "000102030405060708090A0B0C0D0E0F" "hex" To iSuccess
    Loop

    Get ComGetHash Of hoBd "sha256" "base64" To sSha256_base64
    Showln "sha256 hash in base64 format: " sSha256_base64

    Move "AwF2BbOvL6jA5DwmMAc9n6J2Cc8PI6Rj5W079+aKJcIEtPWRzHor0Bvc3aftGM3Jbgj6SXlIC3M3RYS7UZOnfiHKFNZgbxaNT5WwsWooK42ZkC8DBZl0p7OunBUKd5SciUo+TKilioeUkriN3L1Zl9hwi3HVDVqgVo3XXskwIftSqLSFlepTLTmOWj9Y93dp8J4D9RyLtNgFQBc0WB22tyJTsuY56mLcWe1AMF3LizB9OrbwjynF2u16xWlrJdugccz795fJBUV9aQSD+8S3KeqwQhoi8RK1uhD68aGCyaSpBq0NZ8COAkn7MXaF4POxrAAt8udfHM+PRfSOptcH/w==" To sBase64_rsa_sig

    // Get the public key to be used for signature verification.
    Get Create (RefClass(cComChilkatPublicKey)) To hoPubKey
    If (Not(IsComObjectCreated(hoPubKey))) Begin
        Send CreateComObject of hoPubKey
    End
    Get ComLoadFromFile Of hoPubKey "rsaKeys/chilkat-rsa-2048.pem" To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoPubKey To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Get Create (RefClass(cComChilkatRsa)) To hoRsa
    If (Not(IsComObjectCreated(hoRsa))) Begin
        Send CreateComObject of hoRsa
    End
    Get pvComObject of hoPubKey to vPubKey
    Get ComImportPublicKeyObj Of hoRsa vPubKey To iSuccess

    // Verify the hash against the signature.
    Set ComEncodingMode Of hoRsa To "base64"
    Get ComVerifyHashENC Of hoRsa sSha256_base64 "sha256" sBase64_rsa_sig To iSuccess

    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoRsa To sTemp1
        Showln sTemp1
        Showln "Signature invalid."
    End
    Else Begin
        Showln "Signature valid."
    End



End_Procedure