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4

Would it be easier to find collisions, preimages, etc? First note that if you can find preimages for a compressing function (like a hash) you can also find collisions. This means if we can't find collisions, then we also can't find preimages and thelike. Now, the scenario you are describing is called a "freestart collision attack". Freestart collisions are ...

3

How is asymmetric cryptography safe under these conditions? Well, you sort of outlined (but see kelalaka's corrections) how you would use asymmetric crypto to do authentication; that is, to make sure that the message was actually sent from $A$. You ask "how does that provide privacy?". The answer, of course, is "if that's all you do, it doesn't". If we ...

1

Firstly, you misunderstood what is a signature and encryption with the public key. A signature requires a hash then sign paradigm with the senders private key so that any receiver can verify the signature. The RSA paper gave the first idea to digital signatures that were insecure and the Rabin Signature released in 1979 is the fist secure signature that ...

2

If someone has a large set of values: $$B + \epsilon_0, B+\epsilon_1, B+\epsilon_2, …, B+\epsilon_n$$ One can average all these values together. If the values of $\epsilon_0, \epsilon_1, \epsilon_2, …, \epsilon_n$ are independently distributed with a mean of 0, the average of these values will be closer to $B$ (essentially reducing the size of the error ...

0

You're missing that using a KEM for hybrid is not encrypting random garbage. Say you have a chain of ciphertexts $C_1||C_2||\dots|| C_n$, where $C_1 = \mathsf{Enc}_K(k)$, where $k$ is an AES key, and $C_2||\dots||C_n$ is the result of encrypting some stream of plaintexts under the AES key $k$ in some mode of operation. If we can compute \$k = \mathsf{Dec}_K(...

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