Thom
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 Nov 1 comment Distinguish messages I would like to compare the number of strings of length equal or less than $p(n)$ with the number of strings of length $p(n)+n$. Is this a good idea? Oct 31 comment Distinguish messages I want to show that it is not secure when the messages are of different lengths. My thought was this: suppose that the encryption of a single bit cannot be longer than $p(n)$, what do we know about a message of lets say length $p(n)+n$? My idea was to let the adversary select $m_0 \in \{0,1\}$ and $m_1 \in \{0,1\}^{p(n)+n}$. Oct 31 comment Distinguish messages How do I know how big $l_1$ should be? And what is the chance of $m_0$ being encrypted in a ciphertext longer than $l_1$? Oct 31 comment Distinguish messages Thank you. "Now, suppose you have the two messages $||m_0||=l_0$, $||m_1||=l_1$ and $l_0<10Gbits). If you receive a ciphertext shorter than$l_1$you know that$m_1$was encrypted." I guess you meant$m_0\$ in this last sentence? Oct 29 comment Modifications of CBC-MAC @Bob, I still don't understand it. What happens when the message is of length > 2^n? Oct 29 comment Modifications of CBC-MAC @bob, will you please explain 3?