u8vector-blowfish.scm

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|#

;; Blowfish, a simple & reasonably fast symmetric cipher (albeit with high initialization overhead)
;; maximum key length is 56 bytes, minimum 4

(c-declare  #<<end-of-c-declare
#include <openssl/blowfish.h>

#ifndef u_int8_t
typedef unsigned char  u_int8_t;
#endif

// minimal glue for 16 distinct keys
static BF_KEY mykey[16];

void _blf_key(int idx, void *data, int len) {
  BF_set_key(&mykey[idx&15], len, (u_int8_t*)data);
}

void _blf_enc(int idx, void *data, int len) {
  u_int8_t *d=(u_int8_t*)data;
  int blocks=(len>>3);

  int i;
  for (i=0;i<blocks;i++){
    BF_ecb_encrypt(d,d,&mykey[idx&15],BF_ENCRYPT);
    d+=8;
  }
}
void _blf_dec(int idx, void *data, int len) {
  u_int8_t *d=(u_int8_t*)data;
  int blocks=(len>>3);

  int i;
  for (i=0;i<blocks;i++){
    BF_ecb_encrypt(d,d,&mykey[idx&15],BF_DECRYPT);
    d+=8;
  }
}

end-of-c-declare
)

;; maximum key length is 56 bytes, minimum 4
(define (u8vector-setkey-blowfish keyidx vect)
  ((c-lambda (int scheme-object int) void
     "_blf_key(___arg1,___CAST(void*,___BODY_AS(___arg2,___tSUBTYPED)), ___arg3);")
         keyidx vect (u8vector-length vect)))

(define (u8vector-encrypt-blowfish keyidx vect)
  (if (u8vector? vect)
    (let* ((padlen1 (fx- 8 (modulo (fx+ 1 (u8vector-length vect)) 8)))
           (padlen (if (fx= padlen1 8) 0 padlen1))
           (pad (random-u8vector padlen))
           (tmp (u8vector-append (u8vector padlen) vect pad)))
      ((c-lambda (int scheme-object int) void
        "_blf_enc(___arg1,___CAST(void*,___BODY_AS(___arg2,___tSUBTYPED)), ___arg3);") keyidx tmp (u8vector-length tmp))
      tmp
    )
    #f
  ))

(define (u8vector-decrypt-blowfish keyidx vect)
  (if (u8vector? vect)
    (let ((tmp (u8vector-copy vect)))
      ((c-lambda (int scheme-object int) void
        "_blf_dec(___arg1,___CAST(void*,___BODY_AS(___arg2,___tSUBTYPED)), ___arg3);") keyidx tmp (u8vector-length tmp))
      (let ((padlen (u8vector-ref tmp 0)))
        (if (fx> padlen (fx- (u8vector-length tmp) 1))
          #f
          (subu8vector tmp 1 (fx- (u8vector-length tmp) padlen))
        )
      )
    )
    #f
  ))

;; unit tests
;; -----------------

(unit-test "u8vector-blowfish" "1000 random vectors"
  (lambda () (let loop ((n 1000))
    (if (fx= n 0)
      #t
      (if (let* ((keyidx (random-integer 16))
                 (keylen (+ (random-integer 52) 4))
                 (key (random-u8vector keylen))
                 (datalen (random-integer 100000))
                 (data (random-u8vector datalen)))
            (u8vector-setkey-blowfish keyidx key)
            (not (equal? data (u8vector-decrypt-blowfish keyidx (u8vector-encrypt-blowfish keyidx data)))))
        #f
        (loop (fx- n 1)))
    ))
  ))
;; eof