DataFlex

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. DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoSb
    Boolean iCrlfLineEnding
    Integer i
    String sBase64_rsa_sig
    Variant vPubKey
    Handle hoPubKey
    Handle hoRsa
    String sSignedString
    String sTemp1

    Move False To iSuccess

    // Create the same string we previously signed in this example: 
    // RSA Sign utf-8 Bytes of String to get Base64 RSA Signature

    Get Create (RefClass(cComChilkatStringBuilder)) To hoSb
    If (Not(IsComObjectCreated(hoSb))) Begin
        Send CreateComObject of hoSb
    End
    Move True To iCrlfLineEnding

    For i From 0 To 10
        Get ComAppendLine Of hoSb "This is a test." iCrlfLineEnding To iSuccess
    Loop

    Move "gWgpEXQqvXN6wh0MuFXPiw2xCb8cnmdizBT1TD1Tpm2GlJ8gnD59DGSj35GGXk1tM+mCOvMa2uW/9gmz8p6A90JLbn918i/2wKGvcde4wXnzPO7JADSNn2UwYzf3rp4/q/JrHv1GZETRJhABSFqTxOgdmdbEJQE/zijOSctCtQAM2CTb6t2BO8uHKSSUAwPH2cbeWxqsaVRLT4ruk5nZOxhoLgLMSjupiSzbE8zSTkkFOEHD+Mbb2xwg85AI0E4DsUnp+hLwwtS0blesgSyvtBY8oJODJeFcJsR7JDOTPdzHQHgJRl/2A4ij5xT91TpXy7ok43jhT6O9j7Q3qrafIQ==" 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 ComUsePublicKey Of hoRsa vPubKey To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoRsa To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // 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.
    Set ComCharset Of hoRsa To "utf-8"
    Set ComEncodingMode Of hoRsa To "base64"
    Get ComGetAsString Of hoSb To sSignedString
    Get ComVerifyStringENC Of hoRsa sSignedString "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