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(define-module (tiss)
#:use-module (ice-9 string-fun)
#:use-module (hashing md5)
#:use-module (rnrs bytevectors)
#:use-module (ice-9 exceptions)
#:export (tiss
get-hash
starts-with?))
(define (tiss prefix output-prefix suffix)
"Given KEY puzzle key and the desired
OUTPUT-PREFIX, and the current suffix,
incrementally tries hash inputs until
the desired output is achieved.
Throws an exception after 150000 iterations."
;; (display (format #f "suffix is now: ~s\n" suffix))
(when (> suffix 1000000000)
(raise-exception
(make-exception-with-message
(format #f "Exceeded maximum attempts for key ~s!" prefix))))
(let ((output (get-hash prefix (number->string suffix))))
(if (starts-with? output output-prefix)
suffix
(tiss prefix output-prefix (1+ suffix)))))
(define (get-hash prefix suffix)
"Computes the MD5 hash of prefix
combined with suffix."
(md5->string
(md5 (string->utf8
(string-append prefix suffix)))))
(define (starts-with? str prefix)
"Returns #t if STR starts with PREFIX."
(let ((prefix-length (string-length prefix)))
(and (>= (string-length str) prefix-length)
(equal? (substring str 0 prefix-length) prefix))))
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