Cryptanalysis is the study of taking encrypted data, and trying to unencrypt it without use of the key. The other side of cryptography, it is used to break codes by finding weaknesses within them. In addition to being used by hackers with bad intentions, this discipline is also often used by the military. It is also appropriately used by designers of encryption systems to find, and subsequently correct, any weaknesses that may exist in the system under design.
Plaintext is an original text / data which will be converted into a random nonsense text called ciphertext in order to prevent the original message being read by the people out of the recipient. The encryption process consists of an algorithm that produce a different output depending on the specific key being used at the time and a key which value is independent of the plaintext and shared by sender and recipient. The ciphertext can be transformed back to the original plaintext by using a decryption algorithm and the same key that was used for encryption. The security of conventional encryption depends on the secrecy of the key, not the secrecy of the algorithm. It is impractical to decrypt a message based on the ciphertext plus knowledge of the encryption/decryption algorithm. The principal security problem is maintaining the secrecy of the key.
If we look at picture above, with the message X and the encryption key K as input, the encryption algorithm form the ciphertext.
Y=
Ek(X)
X=
Dk(Y)
Security of conventional encryption depends on several factors:
-. The encryption algorithm must be impractical to decrypt a message on the basis of the ciphertext and knowledge of the encryption/decryption algorithm.
-. Secrecy of the key
