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1

In general, you never want to use CRC/weak checksum for any computations on secret material (like keys). CRC is a linear function and by showing CRC of a key, you reveal a lot of equations that hold among the key bits. This is equivalent to showing the same number of bits of the key as the length of the checksum. The proper way of doing it has been ...


2

GOST symmetric cipher uses 256-bit keys to encrypt 64-bit blocks. That means there are many keys which give the same result This is actually incorrect. A block cipher, when given a key, maps $n$-bit plaintext blocks to $n$-bit ciphertext blocks (and vice versa for decryption). Here's a toy example for $n=2$: $E_k(00) = 01 \\ E_k(01) = 10 \\ E_k(10) ...


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This is because the set of possible permutations of 64 bit blocks of plaintext ($2^{64}$ possibilities) to 64 blocks of ciphertext is very high. A key selections just one of these permutations. Even a 256 bit key space is smaller by far than the number of possible permutations. Some plaintext blocks will likely map to the same ciphertext block for a few of ...


1

The https://www.keylength.com/en web site summarizes reports from well-known organizations to give cryptographic key length recommandations for different kind of algorithms. Also note that The lengths provided here are designed to resist mathematic attacks; they do not take algorithmic attacks, hardware flaws, etc. into account. Plus, there is a ...


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No, the security is about identical, as the underlying RSA problem is the same. Besides that, non-repudiation is usually managed differently with regards to legal requirements. Providing confidentiality (encryption) is a rather different use case than non-repudiation (signing a contract). It is also possible to use signatures for authentication rather than ...



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