(SQL Server) RSA Encrypt and Decrypt Credit Card Numbers

SQL Server sample code to RSA public-key encrypt and decrypt credit card numbers. The RSA key is loaded from an unencrypted PKCS8 file. Chilkat provides many ways of setting the key -- loading from both encrypted and unencrypted PEM, PKCS8, DER, PVK, etc. Keys may be loaded from files or in-memory representations. (The RSA component also provides the ability to generate RSA keys.)

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

-- Important: See this note about string length limitations for strings returned by sp_OAMethod calls.
--
CREATE PROCEDURE ChilkatSample
AS
BEGIN
    DECLARE @hr int
    -- Important: Do not use nvarchar(max).  See the warning about using nvarchar(max).
    DECLARE @sTmp0 nvarchar(4000)
    -- This example assumes the Chilkat API to have been previously unlocked.
    -- See Global Unlock Sample for sample code.

    DECLARE @rsa int
    -- Use "Chilkat_9_5_0.Rsa" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Rsa', @rsa OUT
    IF @hr <> 0
    BEGIN
        PRINT 'Failed to create ActiveX component'
        RETURN
    END

    DECLARE @key int
    -- Use "Chilkat_9_5_0.PrivateKey" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.PrivateKey', @key OUT

    -- Load an RSA private key from a file:
    DECLARE @success int
    EXEC sp_OAMethod @key, 'LoadAnyFormatFile', @success OUT, 'rsaPrivateKey.key', ''
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @key, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @rsa
        EXEC @hr = sp_OADestroy @key
        RETURN
      END

    -- Get the key as XML:
    DECLARE @keyXml nvarchar(4000)

    EXEC sp_OAMethod @key, 'GetXml', @keyXml OUT

    -- We'll encrypt with the public key and decrypt with the private
    -- key.  (It's also possible to do the reverse.)
    -- Note: An RSA private key is composed of different parts internally: modulus, exponent, P, Q, etc.
    -- An RSA public-key is a sub-set of the private key.
    -- Therefore, when you have a private key, you really have
    -- both public and private keys.
    EXEC sp_OAMethod @rsa, 'ImportPublicKey', @success OUT, @keyXml
    IF @success <> 1
      BEGIN
        EXEC sp_OAGetProperty @rsa, 'LastErrorText', @sTmp0 OUT
        PRINT @sTmp0
        EXEC @hr = sp_OADestroy @rsa
        EXEC @hr = sp_OADestroy @key
        RETURN
      END

    -- Encrypt a VISA credit card number:
    -- 1234-5678-0000-9999
    DECLARE @ccNumber nvarchar(4000)
    SELECT @ccNumber = '1234567800009999'

    DECLARE @usePrivateKey int
    SELECT @usePrivateKey = 0
    EXEC sp_OASetProperty @rsa, 'EncodingMode', 'base64'
    DECLARE @encryptedStr nvarchar(4000)
    EXEC sp_OAMethod @rsa, 'EncryptStringENC', @encryptedStr OUT, @ccNumber, @usePrivateKey

    PRINT 'Encrypted:'

    PRINT @encryptedStr

    -- Now decrypt:
    DECLARE @rsaDecryptor int
    -- Use "Chilkat_9_5_0.Rsa" for versions of Chilkat < 10.0.0
    EXEC @hr = sp_OACreate 'Chilkat.Rsa', @rsaDecryptor OUT

    EXEC sp_OASetProperty @rsaDecryptor, 'EncodingMode', 'base64'
    EXEC sp_OAMethod @rsaDecryptor, 'ImportPrivateKey', @success OUT, @keyXml

    SELECT @usePrivateKey = 1
    DECLARE @decryptedStr nvarchar(4000)
    EXEC sp_OAMethod @rsaDecryptor, 'DecryptStringENC', @decryptedStr OUT, @encryptedStr, @usePrivateKey


    PRINT 'Decrypted:'

    PRINT @decryptedStr

    -- Important: RSA encryption should only be used to encrypt small amounts of data.
    -- It is typically used for encrypting symmetric encryption
    -- keys such that a symmetric encryption algorithm, such as 
    -- AES is then used to encrypt/decrypt bulk data

    EXEC @hr = sp_OADestroy @rsa
    EXEC @hr = sp_OADestroy @key
    EXEC @hr = sp_OADestroy @rsaDecryptor


END
GO