It is therefore essential that the used encryption/decryption key must be hard to guess and be as long as possible, consequently the set of possible keys will be as long as possible.
The cryptosystem is the encryption algorithm and the set of keys and protocols are what allow its operation.
The cryptanalysis is the science that studies how to force a cryptographic system (cryptosystem). Cryptosystem is the package of all cryptographic algorithms and keys, procedures, protocols, and instructions used for encoding and decoding messages using cryptography.
Most modern ciphers are still safe from cryptanalysis techniques.
The attack on a cryptosystem has the goal of forcing the system. The method chosen and the danger depends on the information available to the cryptanalyst.