(DataFlex) Charset Considerations when RSA Encrypting Strings

When encrypting strings, character encoding can be an issue. Encryption algorithms operate on binary data. If for example, your string includes a character such as é, the bytes used to represent it depend on the character encoding. In an "iso" encoding such as iso-8859-1, or in a "windows" encoding, such as "windows-1252", the é is represented by a single byte. In Unicode however, whether it's utf-8 or ucs-2, the é is represented by 2 bytes. When encrypting strings, the RSA component will first convert the string to the character encoding indicated by the Charset property. When decrypting strings, the RSA component converts from the character encoding indicated by the Charset property to the application's expected charset. In VB6 for example, this would be Unicode. In C++, it's ANSI. In Java, it's utf-8.

Note: This example requires Chilkat v11.0.0 or greater.

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

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoRsa
    String sPubKeyXml
    Variant vPubKey
    Handle hoPubKey
    String sPlainText
    Boolean iUsePrivateKey
    String sEncryptedStr
    String sTemp1

    Move False To iSuccess

    // This example assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    Get Create (RefClass(cComChilkatRsa)) To hoRsa
    If (Not(IsComObjectCreated(hoRsa))) Begin
        Send CreateComObject of hoRsa
    End

    // RSA public key in XML format:
    Move "<RSAPublicKey><Modulus>of3im3mRgd2NLXIGoK6uYLg6jj0Ug2b42rnqa5Tbwz2ieFqMJqt+++x2oqLYGurlz49nt+7/785g3XYWqoka4u9c9zul6YubIjnBM72dQy7rEkEfbUxgjcxqXyjZFx+FpaxFUecLu688XEu+9UA42VKiCgcl+E7TrqnfeeYpNXc=</Modulus><Exponent>AQAB</Exponent></RSAPublicKey>" To sPubKeyXml

    Get Create (RefClass(cComChilkatPublicKey)) To hoPubKey
    If (Not(IsComObjectCreated(hoPubKey))) Begin
        Send CreateComObject of hoPubKey
    End
    Get ComLoadFromString Of hoPubKey sPubKeyXml To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoPubKey To sTemp1
        Showln sTemp1
        Procedure_Return
    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

    // Use the utf-8 character encoding.  When encrypting, the
    // plain text is first converted to utf-8 bytes and then
    // RSA encrypted.
    Set ComCharset Of hoRsa To "utf-8"

    // Encrypt a string and return the encrypted data base64-encoded:
    Set ComEncodingMode Of hoRsa To "base64"

    Move "éééé" To sPlainText

    Move False To iUsePrivateKey
    Get ComEncryptStringENC Of hoRsa sPlainText iUsePrivateKey To sEncryptedStr
    Showln sEncryptedStr


End_Procedure