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; 5-5-2005 / Greg Pettyjohn

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;  - It was failing for strings of length 56 bytes i.e. when the length
;    in bits was congruent 448 modulo 512. Changed step 1 to fix this.
;    According to RFC 1321, the message should still be padded in this
;    case.

original commit: a52987da2a6deba95b03752cc8930428bca8c580
This commit is contained in:
Greg Pettyjohn 2005-03-05 23:59:29 +00:00
parent 7a876fbfdd
commit b44c2dd378
1 changed files with 22 additions and 10 deletions
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32
collects/mzlib/md5.ss
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@ -1,5 +1,5 @@
(module md5 mzscheme
(provide md5)
(provide md5)
;;; -*- mode: scheme; mode: font-lock -*-
;;;
@ -47,6 +47,14 @@
; - Trivial port to PLT. Rewrote the word macro to syntax-rules.
; Larceny primitives written as syntax-rules macros exanding
; to their PLT name.
; 5-5-2005 / Greg Pettyjohn
; - It was failing for strings of length 56 bytes i.e. when the length
; in bits was congruent 448 modulo 512. Changed step 1 to fix this.
; According to RFC 1321, the message should still be padded in this
; case.
;;; Summary
; This is an implementation of the md5 message-digest algorithm
@ -257,24 +265,25 @@
;; We allways append a 1 bit and then append the proper numbber of 0's.
;; NB: 448 bits is 14 words and 512 bits is 16 words
;; step1 : (list byte) -> (list byte)
(define (step1 message)
(let ((zero-bits-to-append (modulo (- 448 (* 8 (length message))) 512)))
(let* ([z-b-t-a (modulo (- 448 (* 8 (length message))) 512)]
[zero-bits-to-append (if (zero? z-b-t-a) 512 z-b-t-a)])
(append message
(cons #x80 ; The byte containing the 1 bit => one less
(cons #x80 ; The byte containing the 1 bit => one less
; 0 byte to append
(vector->list
(make-vector
(quotient (- zero-bits-to-append 1) 8) 0))))))
(vector->list
(make-vector
(quotient (- zero-bits-to-append 1) 8) 0))))))
;; Step 2 - Append Length
;; A 64 bit representation of the bit length b of the message before
;; the padding of step 1is appended. Lower word first.
;; the padding of step 1 is appended. Lower word first.
;; step2 : number (list byte) -> (list word)
;; org-len is the length of the original message in number of bits
(define (step2 org-len padded-message)
(let* ((b org-len)
(define (step2 original-length padded-message)
(let* ((b original-length)
(lo (remainder b #x100000000))
(hi (remainder (quotient b #x100000000) #x100000000)))
(bytes->words
@ -296,6 +305,8 @@
;; step4 : (list word) -> "(list word word word word)"
(define (step4 message)
(define (loop A B C D message)
(if (null? message)
(list A B C D)
@ -405,6 +416,7 @@
(define (step5 l)
(define hex #(48 49 50 51 52 53 54 55 56 57 97 98 99 100 101 102))
(define (number->hex n)