| … | |
… | |
| 21 | =cut |
21 | =cut |
| 22 | |
22 | |
| 23 | package Digest::Hashcash; |
23 | package Digest::Hashcash; |
| 24 | |
24 | |
| 25 | use Time::Local; |
25 | use Time::Local; |
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26 | use Time::HiRes; |
| 26 | |
27 | |
| 27 | require XSLoader; |
28 | require XSLoader; |
| 28 | |
29 | |
| 29 | no warnings; |
30 | no warnings; |
| 30 | |
31 | |
| 31 | $VERSION = 0.01; |
32 | $VERSION = 0.02; |
| 32 | |
33 | |
| 33 | XSLoader::load Digest::Hashcash, $VERSION; |
34 | XSLoader::load Digest::Hashcash, $VERSION; |
| 34 | |
35 | |
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36 | =item $secs = estimate_time $size |
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37 | |
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38 | Estimate the average time necessary to calculate a token of the given |
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39 | size. |
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40 | |
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41 | See also C<estimate_size>. |
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42 | |
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43 | =item $size = estimate_size $time[, $min] |
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44 | |
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45 | Estimate the size that can be calculated in the given time (which is an |
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46 | upper bound). The function will not return a size less then C<min>. |
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47 | |
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48 | Estimating the time to be used can go wrong by as much as 50% (but is |
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49 | usually quite accurate), and the estimation itself can take as much as a |
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50 | second on slower (<pentium) machines, but faster machines (1Ghz P3 for |
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51 | example) usually handle it within a hundredth of a second or so. |
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52 | |
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53 | The estimation will be done only once, so you can call this fucntion as |
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54 | often as you like without incuring the overhead everytime. |
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55 | |
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56 | =cut |
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57 | |
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58 | my $rounds; |
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59 | |
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60 | sub _rounds { |
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61 | $rounds ||= &_estimate_rounds(); |
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62 | } |
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63 | |
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64 | sub estimate_time { |
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65 | my ($size) = @_; |
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66 | 2**$size / &_rounds; |
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67 | } |
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68 | |
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69 | sub estimate_size { |
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70 | my ($time, $min) = @_; |
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71 | $time = (log $time * $rounds) / log 2; |
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72 | $time < $min ? $min : int $time; |
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73 | } |
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74 | |
| 35 | =item $cipher = new [param => value...] |
75 | =item $cipher = new [param => value...] |
| 36 | |
76 | |
| 37 | =over 4 |
77 | =over 4 |
| 38 | |
78 | |
| 39 | =item size => 20 + some |
79 | =item size => 18 |
| 40 | |
80 | |
| 41 | The number of collisions, in bits. Every bit increases the time to create |
81 | The number of collisions, in bits. Every bit increases the time to create |
| 42 | the token (and thus the cash) by two. |
82 | the token (and thus the cash) by two. |
| 43 | |
83 | |
| 44 | =item uid => "" |
84 | =item uid => "" |
