Block Ciphers

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Block ciphers 🔗

A symmetric block cipher consists of multiple

rounds

, made up of

substitutions

and

permutations

controlled by a

key

.

Parameters and design characteristics of symmetric block ciphers:

An encryption scheme can be considered computationally secure if the resulting ciphertext satisfies one or both of the following conditions.

The cost of breaking the cipher exceeds the value of the encrypted information.
The time required to break the cipher exceeds the useful lifetime of the information.