Lecture_2

Encryption for Confidentiality
Aim:assure confidential information not made available to unauthorized individuals (data confidentiality)
How:encrypt the original data; anyone can see the encrypted data, but only authorized individuals can decrypt to see the original data
Used for both sending data a cross network and storing data on a computer system
Definitions
Plaintext: original message
Ciphertext: encrypted or coded message
Encryption: convert from plaintext to ciphertext (enciphering)
Decryption: restore the plaintext from ciphertext (deciphering)
Key: information used in cipher known only to sender/receiver
Cipher: a particular algorithm (cryptographic system)
Cryptography: study of algorithms used for encryption
Cryptanalysis: study of techniques for decryption without knowledge of plaintext
Cryptology: areas of cryptography and cryptanalysis
Requirements for secure use of symmetric encryption:
Strong encryption algorithm: Given the algorithm and ciphertext, an attacker cannot obtain key or plaintext
Sender/receiver know secret key (and keep it secret)
Assumptions:
Cipher is known
Secure channel to distribute keys