Main implementation done. Need docs and tests.

extra/hashcash/authors.txt

@@ -0,0 +1 @@
+Diego Martinelli

extra/hashcash/hashcash.factor

@@ -1,4 +1,90 @@
-! Copyright (C) 2009 Your name.
+! Copyright (C) 2009 Diego Martinelli.
 ! See http://factorcode.org/license.txt for BSD license.
-USING: ;
+USING: accessors byte-arrays calendar calendar.format 
+checksums checksums.openssl classes.tuple 
+fry kernel make math math.functions math.parser math.ranges 
+present random sequences splitting strings syntax ;
 IN: hashcash
+
+! Hashcash implementation
+! Reference materials listed below:
+! 
+! http://hashcash.org
+! http://en.wikipedia.org/wiki/Hashcash
+! http://www.ibm.com/developerworks/linux/library/l-hashcash.html?ca=dgr-lnxw01HashCash
+! 
+! And the reference implementation (in python):
+! http://www.gnosis.cx/download/gnosis/util/hashcash.py
+
+<PRIVATE
+
+! Return a string with today's date in the form YYMMDD
+: get-date ( -- str )
+    now [ year>> 100 mod pad-00 ] 
+        [ month>> pad-00 ] 
+        [ day>> pad-00 ] tri 3append ;
+
+! Random salt is formed by ascii characters
+! between 33 and 126
+: available-chars ( -- seq )
+    33 126 [a,b] [ CHAR: : = not ] filter ;
+
+PRIVATE>
+
+! Generate a 'length' long random salt
+: salt ( length -- salted )
+    available-chars '[ _ random ] "" replicate-as ;
+
+TUPLE: hashcash version bits date resource ext salt suffix ;
+
+: <hashcash> ( -- tuple )
+    hashcash new
+        1 >>version
+        20 >>bits
+        get-date >>date
+        8 salt >>salt ;
+
+M: hashcash string>> 
+    tuple-slots [ present ] map ":" join ;
+
+<PRIVATE
+
+: sha1-checksum ( str -- bytes )
+    openssl-sha1 checksum-bytes ; inline
+
+: set-suffix ( tuple guess -- tuple )
+    >hex >>suffix ;
+
+: get-bits ( bytes -- str )
+    [ >bin 8 CHAR: 0 pad-head ] { } map-as concat ;
+
+: checksummed-bits ( tuple -- relevant-bits )
+    dup string>> sha1-checksum
+    swap bits>> 8 / ceiling head get-bits ;
+
+: all-char-zero? ( seq -- ? )
+    [ CHAR: 0 = ] all? ; inline
+
+: valid-guess? ( checksum tuple -- ? )
+    bits>> head all-char-zero? ;
+
+: (mint) ( tuple counter -- tuple ) 
+    2dup set-suffix checksummed-bits pick 
+    valid-guess? [ drop ] [ 1+ (mint) ] if ;
+
+PRIVATE>
+
+: mint* ( tuple -- str )
+    0 (mint) string>> ;
+
+: mint ( resource -- str )
+    <hashcash>
+        swap >>resource
+    mint* ;
+
+! One might wanna add check based on the date,
+! passing a 'good-until' duration param
+: check-stamp ( stamp -- ? )
+    dup ":" split [ sha1-checksum get-bits ] dip
+    second string>number head all-char-zero? ;
+