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frohoff/terse-rc4.rb

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terse ruby rc4 (161 chars, 154 chars not counting proc/param overhead) for https://twitter.com/matthew_d_green/status/524966294492577792
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terse-rc4.rb
->t,k{s=*0..255;j=0;m=256;m.times{|i|j=(j+s[i]+k[i%k.size])%m;s[i],s[j]=s[j],s[i]};i=j=0;t.map{|b|i=(i+1)%m;j=(j+s[i])%m;s[i],s[j]=s[j],s[i];b^s[(s[i]+s[j])%m]}}
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frohoff commented Oct 22, 2014 

pry(main)> ->t,k{s=*0..255;j=0;m=256;m.times{|i|j=(j+s[i]+k[i%k.size])%m;s[i],s[j]=s[j],s[i]};i=j=0;t.map{|b|i=(i+1)%m;j=(j+s[i])%m;s[i],s[j]=s[j],s[i];b^s[(s[i]+s[j])%m]}}[[1,2,3,4],[5,6,7,8]]
=> [247, 228, 31, 141]

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