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@dmb2
Created June 30, 2015 14:28
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# Cipher text is a bytestring
# bi is the block index, or which block to edit. Flipping a bit in this block will result in a one bit edit in the bi+1 plaintext block
# i is the targeted bit's index
# z is the array of decoded bytes.
# The idea here is to target bit i, but also flip the bits of previously discovered bytes.
def flip_bit(cipher_text,bi,i,z)
bsize=16
i.times do |j|
tb=(z[j-1]==nil) ? 0 : z[j-1]
cb=cipher_text.bytes()[bi*bsize-j-1]
cipher_text[bi*bsize-j-1]=(cb^tb^i).chr
end
return cipher_text
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