; data encryption standard
(define (vector-map proc . vecs)
(define (elt i)
(lambda (vec)
(vector-ref vec i)))
(let* ((len (vector-length (car vecs)))
(result (make-vector len)))
(do ((i 0 (+ i 1))) ((= i len) result)
(vector-set! result i
(apply proc (map (elt i) vecs))))))
(define (vector-permute rule vec)
(let* ((len (vector-length rule))
(result (make-vector len)))
(do ((i 0 (+ i 1))) ((= i len) result)
(vector-set! result i
(vector-ref vec (vector-ref rule i))))))
(define (vector-cycle shift vec)
; positive => left, negative => right
(let* ((len (vector-length vec))
(result (make-vector len)))
(do ((i 0 (+ i 1))) ((= i len) result)
(let ((j (modulo (+ i shift) len)))
(vector-set! result i
(vector-ref vec j))))))
(define (vector-slice vec start len)
(let ((result (make-vector len)))
(do ((i 0 (+ i 1))) ((= i len) result)
(vector-set! result i
(vector-ref vec (+ i start))))))
(define (vector-slice-by n vec)
(let* ((len (vector-length vec)))
(let loop ((k 0) (result '()))
(if (= k len) (reverse result)
(loop (+ k n) (cons (vector-slice vec k n) result))))))
(define (vector-append . vecs)
(let* ((len (apply + (map vector-length vecs)))
(result (make-vector len)))
(let loop ((i 0) (j 0) (vecs vecs))
(cond ((null? vecs) result)
((= (vector-length (car vecs)) j)
(loop i 0 (cdr vecs)))
(else (vector-set! result i
(vector-ref (car vecs) j))
(loop (+ i 1) (+ j 1) vecs))))))
(define (vector-xor vec1 vec2)
(define (xor a b) (if (= a b) 0 1))
(vector-map xor vec1 vec2))
(define (undigits ds . args)
(let ((b (if (null? args) 10 (car args))))
(let loop ((ds ds) (n 0))
(if (null? ds) n
(loop (cdr ds) (+ (* n b) (car ds)))))))
(define (n->bits n)
(let ((bv (list->vector '((0 0 0 0) (0 0 0 1) (0 0 1 0) (0 0 1 1)
(0 1 0 0) (0 1 0 1) (0 1 1 0) (0 1 1 1) (1 0 0 0) (1 0 0 1)
(1 0 1 0) (1 0 1 1) (1 1 0 0) (1 1 0 1) (1 1 1 0) (1 1 1 1)))))
(vector-ref bv n)))
(define (char->bits c)
(n->bits (- (char->integer (char-upcase c)) (if (char-numeric? c) 48 55))))
(define (bits->char bits)
(let ((n (undigits (vector->list bits) 2)))
(integer->char (+ n (if (< n 10) 48 55)))))
(define (hex->bits hex)
(list->vector (apply append (map char->bits (string->list hex)))))
(define (bits->hex vec)
(list->string (map bits->char (vector-slice-by 4 vec))))
(define (ascii->bits txt)
(list->vector
(apply append
(map (lambda (c)
(let ((x (char->integer c)))
(append (n->bits (quotient x 16))
(n->bits (modulo x 16)))))
(string->list txt)))))
(define (bits->ascii bits)
(list->string (map integer->char
(map (lambda (v) (undigits (vector->list v) 2))
(vector-slice-by 8 bits)))))
(define (check-parity? key)
(let loop ((ks (vector-slice-by 8 key)))
(cond ((null? ks) #t)
((even? (apply + (vector->list (car ks)))) #f)
(else (loop (cdr ks))))))
(define (pc1 key)
(let ((rule #(
57 49 41 33 25 17 9 1 58 50 42 34 26 18
10 2 59 51 43 35 27 19 11 3 60 52 44 36
63 55 47 39 31 23 15 7 62 54 46 38 30 22
14 6 61 53 45 37 29 21 13 5 28 20 12 4)))
(vector-permute (vector-map sub1 rule) key)))
(define (ls i key)
(let ((rule #(1 1 2 2 2 2 2 2 1 2 2 2 2 2 2 1)))
(vector-cycle (vector-ref rule i) key)))
(define (pc2 key)
(let ((rule #(
14 17 11 24 1 5 3 28 15 6 21 10
23 19 12 4 26 8 16 7 27 20 13 2
41 52 31 37 47 55 30 40 51 45 33 48
44 49 39 56 34 53 46 42 50 36 29 32)))
(vector-permute (vector-map sub1 rule) key)))
(define (key-schedule key)
(let ((c (make-vector 17 #f))
(d (make-vector 17 #f))
(k (make-vector 17 #f))
(c0d0 (pc1 key)))
(vector-set! c 0 (vector-slice c0d0 0 28))
(vector-set! d 0 (vector-slice c0d0 28 28))
(do ((i 1 (+ i 1))) ((< 16 i) k)
(vector-set! c i (ls (- i 1) (vector-ref c (- i 1))))
(vector-set! d i (ls (- i 1) (vector-ref d (- i 1))))
(vector-set! k i (pc2 (vector-append
(vector-ref c i)
(vector-ref d i)))))))
(define (ip data)
(let ((rule #(
58 50 42 34 26 18 10 2 60 52 44 36 28 20 12 4
62 54 46 38 30 22 14 6 64 56 48 40 32 24 16 8
57 49 41 33 25 17 9 1 59 51 43 35 27 19 11 3
61 53 45 37 29 21 13 5 63 55 47 39 31 23 15 7)))
(vector-permute (vector-map sub1 rule) data)))
(define (e data)
(let ((rule #(
32 1 2 3 4 5 4 5 6 7 8 9
8 9 10 11 12 13 12 13 14 15 16 17
16 17 18 19 20 21 20 21 22 23 24 25
24 25 26 27 28 29 28 29 30 31 32 1)))
(vector-permute (vector-map sub1 rule) data)))
(define (s vec)
(define (b->s j)
(let* ((sbox #(
#(14 4 13 1 2 15 11 8 3 10 6 12 5 9 0 7 ; 1
0 15 7 4 14 2 13 1 10 6 12 11 9 5 3 8
4 1 14 8 13 6 2 11 15 12 9 7 3 10 5 0
15 12 8 2 4 9 1 7 5 11 3 14 10 0 6 13)
#(15 1 8 14 6 11 3 4 9 7 2 13 12 0 5 10 ; 2
3 13 4 7 15 2 8 14 12 0 1 10 6 9 11 5
0 14 7 11 10 4 13 1 5 8 12 6 9 3 2 15
13 8 10 1 3 15 4 2 11 6 7 12 0 5 14 9)
#(10 0 9 14 6 3 15 5 1 13 12 7 11 4 2 8 ; 3
13 7 0 9 3 4 6 10 2 8 5 14 12 11 15 1
13 6 4 9 8 15 3 0 11 1 2 12 5 10 14 7
1 10 13 0 6 9 8 7 4 15 14 3 11 5 2 12)
#( 7 13 14 3 0 6 9 10 1 2 8 5 11 12 4 15 ; 4
13 8 11 5 6 15 0 3 4 7 2 12 1 10 14 9
10 6 9 0 12 11 7 13 15 1 3 14 5 2 8 4
3 15 0 6 10 1 13 8 9 4 5 11 12 7 2 14)
#( 2 12 4 1 7 10 11 6 8 5 3 15 13 0 14 9 ; 5
14 11 2 12 4 7 13 1 5 0 15 10 3 9 8 6
4 2 1 11 10 13 7 8 15 9 12 5 6 3 0 14
11 8 12 7 1 14 2 13 6 15 0 9 10 4 5 3)
#(12 1 10 15 9 2 6 8 0 13 3 4 14 7 5 11 ; 6
10 15 4 2 7 12 9 5 6 1 13 14 0 11 3 8
9 14 15 5 2 8 12 3 7 0 4 10 1 13 11 6
4 3 2 12 9 5 15 10 11 14 1 7 6 0 8 13)
#( 4 11 2 14 15 0 8 13 3 12 9 7 5 10 6 1 ; 7
13 0 11 7 4 9 1 10 14 3 5 12 2 15 8 6
1 4 11 13 12 3 7 14 10 15 6 8 0 5 9 2
6 11 13 8 1 4 10 7 9 5 0 15 14 2 3 12)
#(13 2 8 4 6 15 11 1 10 9 3 14 5 0 12 7 ; 8
1 15 13 8 10 3 7 4 12 5 6 11 0 14 9 2
7 11 4 1 9 12 14 2 0 6 10 13 15 3 5 8
2 1 14 7 4 10 8 13 15 12 9 0 3 5 6 11)))
(m1 (vector-ref vec (* j 6)))
(m2 (vector-ref vec (+ (* j 6) 5)))
(m (undigits (list m1 m2) 2))
(n (undigits (vector->list (vector-slice vec (+ (* j 6) 1) 4)) 2)))
(vector-ref (vector-ref sbox j) (+ (* m 16) n))))
(let loop ((j 0) (result '()))
(if (= j 8)
(list->vector (apply append (map n->bits (reverse result))))
(loop (+ j 1) (cons (b->s j) result)))))
(define (p data)
(let ((rule #(
16 7 20 21 29 12 28 17 1 15 23 26 5 18 31 10
2 8 24 14 32 27 3 9 19 13 30 6 22 11 4 25)))
(vector-permute (vector-map sub1 rule) data)))
(define (fp data)
(let ((rule #(
40 8 48 16 56 24 64 32 39 7 47 15 55 23 63 31
38 6 46 14 54 22 62 30 37 5 45 13 53 21 61 29
36 4 44 12 52 20 60 28 35 3 43 11 51 19 59 27
34 2 42 10 50 18 58 26 33 1 41 9 49 17 57 25)))
(vector-permute (vector-map sub1 rule) data)))
(define (f x k) (p (s (vector-xor (e x) k))))
(define (encipher ks block)
(let ((l (make-vector 17 #f)) (r (make-vector 17 #f)) (l0r0 (ip block)))
(vector-set! l 0 (vector-slice l0r0 0 32))
(vector-set! r 0 (vector-slice l0r0 32 32))
(do ((i 1 (+ i 1)))
((< 16 i) (fp (vector-append (vector-ref r 16) (vector-ref l 16))))
(vector-set! l i (vector-ref r (- i 1)))
(vector-set! r i
(vector-xor (vector-ref l (- i 1))
(f (vector-ref r (- i 1)) (vector-ref ks i)))))))
(define (decipher ks block)
(let ((l (make-vector 17 #f)) (r (make-vector 17 #f)) (r16l16 (ip block)))
(vector-set! r 16 (vector-slice r16l16 0 32))
(vector-set! l 16 (vector-slice r16l16 32 32))
(do ((i 16 (- i 1)))
((= i 0) (fp (vector-append (vector-ref l 0) (vector-ref r 0))))
(vector-set! r (- i 1) (vector-ref l i))
(vector-set! l (- i 1)
(vector-xor (vector-ref r i)
(f (vector-ref l i) (vector-ref ks i)))))))
(display
(bits->hex
(encipher
(key-schedule (hex->bits "0123456789ABCDEF"))
(ascii->bits "ProgPrax"))))
(newline)
(display
(bits->ascii
(decipher
(key-schedule (hex->bits "0123456789ABCDEF"))
(hex->bits "CC99EA46B16E2890"))))