Name: Anonymous 2013-05-15 11:43
Suppose two english language messages A and B are encrypted with the same one time pad P: X=A^P and Y=B^P.
Then X^Y=(A^P)^(B^P)=A^B so we can try to guess which words are in A and B and xor it with that to see if we get a word back to chip away at decoding the cyphertext.
The difficulty is that the words overlap, they don't line up easily. For example the messages might be like this:
---- ---------- --- ----- -------- -------- -------
-- ------ ------- ---- ---- --- ------ -------- ---
Then X^Y=(A^P)^(B^P)=A^B so we can try to guess which words are in A and B and xor it with that to see if we get a word back to chip away at decoding the cyphertext.
The difficulty is that the words overlap, they don't line up easily. For example the messages might be like this:
---- ---------- --- ----- -------- -------- -------
-- ------ ------- ---- ---- --- ------ -------- ---