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1

If you are imagining something like 256+ bits of key -> SHA-256 -> one block keystream that you XOR with the plaintext, that is indeed almost the same as one-time pad. However, there is no advantage to doing that, considering you might as well have used the original key directly as a one-time pad. If, instead you use a password-based hash, a dictionary ...


6

A simplified* Carter-Wegman MAC could be defined as: $$ t=\sum_{i=1}^n {k_1^i m_i} + k_2 \pmod p$$ $p$ is a sufficently large prime (e.g. 256 bits). You must choose a new truly random $k_2$ uniformly from $0\leq k_2 <p$. It acts as a one-time-pad that prevents an attacker who sees the tag $t$ from learning anything about $k_1$. The polynomial $\sum {...


11

While the one time pad seems obvious, I am not sure about Carter-Wegman-Style message auth. What they are talking about is a Carter-Wegman authentication method that uses a stream of random bits as a part of the process (just like a one time pad uses a stream of random bits to encrypt). Normally, when we implement CW, we use some almost universal (au) ...



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