At What Point Does Attack Become Practical

Question

At What Point Does Attack Become Practical?

Answer 1

There is no simple answer to this question because it is only depends on many distinct factors. Not only should the work and computational resources needed by the cryptanalyst be rational, however the amount and type of data needed for the attack to be successful should also be taken in account.

One categorization distinguishes among cryptanalytic attacks consistent with the data they need in the following manner: selected plaintext or chosen ciphertext, recognized plaintext, and ciphertext-only. (This categorization is not specific to secret-key ciphers and can be applied to cryptanalytic attacks on any cryptographic.)