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.

Download Chilkat RSA Public-Key Encryption ActiveX

CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    DECLARE @rsa int
    EXEC @hr = sp_OACreate 'Chilkat.Rsa', @rsa OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    DECLARE @success int

    EXEC sp_OAMethod @rsa, 'UnlockComponent', @success OUT, 'Anything for 30-day trial'
    IF @success <> 1
      BEGIN
        PRINT 'RSA component unlock failed'
        RETURN
      END

    --  RSA public key in XML format:
    DECLARE @publicKey nvarchar(4000)

    SELECT @publicKey = '<RSAKeyValue><Modulus>of3im3mRgd2NLXIGoK6uYLg6jj0Ug2b42rnqa5Tbwz2ieFqMJqt+++x2oqLYGurlz49nt+7/785g3XYWqoka4u9c9zul6YubIjnBM72dQy7rEkEfbUxgjcxqXyjZFx+FpaxFUecLu688XEu+9UA42VKiCgcl+E7TrqnfeeYpNXc=</Modulus><Exponent>AQAB</Exponent></RSAKeyValue>'

    EXEC sp_OAMethod @rsa, 'ImportPublicKey', NULL, @publicKey

    --  Use the utf-8 character encoding.  When encrypting, the
    --  plain text is first converted to utf-8 bytes and then
    --  RSA encrypted.
    EXEC sp_OASetProperty @rsa, 'Charset', 'utf-8'

    --  Encrypt a string and return the encrypted data base64-encoded:
    EXEC sp_OASetProperty @rsa, 'EncodingMode', 'base64'

    DECLARE @plainText nvarchar(4000)

    SELECT @plainText = 'éééé'

    DECLARE @usePrivateKey int

    SELECT @usePrivateKey = 0
    DECLARE @encryptedStr nvarchar(4000)

    EXEC sp_OAMethod @rsa, 'EncryptStringENC', @encryptedStr OUT, @plainText, @usePrivateKey
    PRINT @encryptedStr
END
GO