implement cipher module

[Matthias Brantner]

The set of cryptography modules should be extended with a new module to do symmetric and asymmetric encryption and decryption. The implementation should be based on openssl (as hmac and hash) also do.

Here is a proposal for the external functions that should be provided by this module.

module namespace cipher = "http://www.zorba-xquery.com/modules/cryptography/cipher";

declare function cipher:encrypt(
 $input as xs:string,
 $key as xs:string,
 $algo as xs:string, (: "algorithm/mode/padding" or "algorithm")
 $options) as xs:base64Binary external;

declare function cipher:encrypt-binary(
 $input as xs:base64Binary,
 $key as xs:base64Binary,
 $algo as xs:string, (: "algorithm/mode/padding" or "algorithm")
 $options) as xs:base64Binary external;

declare function cipher:decrypt(
 $input as xs:base64Binary,
 $key as xs:string,
 $algo as xs:string, (: "algorithm/mode/padding" or "algorithm")
 $options) as xs:string external;

declare function cipher:decrypt-binary(
 $input as xs:base64Binary,
 $key as xs:base64Binary,
 $algo as xs:string, (: "algorithm/mode/padding" or "algorithm")
 $options) as xs:base64Binary external;

$options may specify
- iv
- key encoding if key is a string (e.g. PKCS8)

We might want to add more convenience functions (e.g. for encryption using a particular algorithm) to the module but those should be implemented in XQuery.

To start with, the module should implement AES, DES, RSA, and DSA.

[Matthias Brantner (matthias-brantner)]

The en- and decryption of and to strings assumes that the string is UTF-8 encoded. If the user wants to encrypt a string in an encoding other than UTF-8, he should use the base64:encode($string, $encoding) function (which doesn't exist, yet) to get a base64 item (or the other way around for decrypt).