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NAME |
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Digest::Hashcash - generate Hashcashes (http://www.hashcash.org) |
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SYNOPSIS |
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use Digest::Hashcash; |
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DESCRIPTION |
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This module implements the hashcash hash (or digest, although it's not |
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clearly a digest). For all your information needs please visit |
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http://www.hashcash.org. |
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|
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One thing to note about this module is that it requires ISO C99 support, |
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both in your compiler and your standard library. If you don't have a |
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compiler that supports ISO C, get gcc at http://gcc.gnu.org/ :) |
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|
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$secs = estimate_time $size |
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Estimate the average time necessary to calculate a token of the |
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given size. |
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See also "estimate_size". |
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$size = estimate_size $time[, $min] |
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Estimate the size that can be calculated in the given time (which is |
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an upper bound). The function will not return a size less then |
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"min". |
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|
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Estimating the time to be used can go wrong by as much as 50% (but |
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is usually quite accurate), and the estimation itself can take as |
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much as a second on slower (<pentium) machines, but faster machines |
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(1Ghz P3 for example) usually handle it within a hundredth of a |
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second or so. |
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|
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The estimation will be done only once, so you can call this fucntion |
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as often as you like without incuring the overhead everytime. |
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|
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$cipher = new Digest::Hashcash [param => value...] |
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|
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size => 18 |
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The number of collisions, in bits. Every bit increases the time |
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to create the token (and thus the cash) by two. |
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|
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uid => "" |
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A string used to make the token more unique (e.g. the senders |
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address) and reduce token collisions. The string must only |
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contain characters valid for the trial part of the token, e.g. |
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uuencoded, base64 or e-mail-address-parts are useful here. |
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|
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extrarand => 0 |
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The extra bytes of randomness to add to the token in addition to |
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the standard amount. Each byte adds a little bit over 6 bit of |
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randomness to the token. |
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|
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The standard amount of randomness is 8 (> 51 bits of |
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randomness). |
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|
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timestamp => 0 |
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The timestamp to use. A value of 0 (the default) means to use |
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the current time. |
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|
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$token = $cipher->hash ($data [, param => value...]) |
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Creates and returns a new token. This can take some time. |
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Any additional parameters are interpreted the same way as arguments |
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to "new". |
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$prefix = $cipher->verify ($token [, param => value...])) |
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Checks the given token and returns true if the token has the minimum |
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number of prefix bits, or false otherwise. The value returned is |
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actually the number of collisions, so to find the number of |
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collisions bits specify "collisions => 0". |
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|
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Any additional parameters are interpreted the same way as arguments |
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to "new". |
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|
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$resource = $cipher->resource ($token) |
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Returns the resource part, or "undef". |
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|
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$tstamp = $ciper->timestamp ($token) |
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Returns the timestamp part (in the same format as perl's "time"), or |
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"undef". |
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SEE ALSO |
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<http://www.hashcash.org>. |
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|
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SUPPORT FOR THE PERL MULTICORE SPECIFICATION |
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This module supports the perl multicore specification |
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(<http://perlmulticore.schmorp.de/>) for token generation of any length |
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and size. |
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|
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BUGS |
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* There is a y2k+100 problem, as I always assume the same as Time::Local. |
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This is a problem with the hashcash specification, which specifies |
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years as 2 digits :( |
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|
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AUTHOR |
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Marc Lehmann <schmorp@schmorp.de> |
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http://home.schmorp.de |
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