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chicken-scheme-hmac/hmac.scm

30 lines
987 B
Scheme

; author: Thomas Hintz
; email: t@thintz.com
; license: bsd
(module hmac
(hmac)
(import scheme chicken srfi-4 srfi-13)
(use message-digest-port)
(define (hmac key digest-primitive #!optional (block-size 64))
(when (> (string-length key) block-size)
(set! key (call-with-output-digest digest-primitive (cut display key <>) 'string)))
(set! key (string-pad-right key block-size (integer->char 0)))
(let ((ipad (string-map (lambda (c) (integer->char (bitwise-xor (char->integer c) #x36))) key))
(opad (string-map (lambda (c) (integer->char (bitwise-xor (char->integer c) #x5c))) key)))
(lambda (message)
(call-with-output-digest
digest-primitive
(cut display
(string-append opad
(call-with-output-digest
digest-primitive
(cut display (string-append ipad message) <>)
'string))
<>)
'string))))
)