Encryption Basics Module 7 Section 2

History of Encryption Secret - NSA National Security Agency –has powerful computers - break codes –monitors all communications between US and other countries and within –Designs codes and breaks codes

History Developed by Diffie & Hellman Two mathematically related keys –to encrypt –to decrypt Knowing the key to encrypt does not help decrypt Each person has their own key pair

History The encrypting key can become public Public key - encrypt Private key - decrypt Senders can ID the recipients public key to encrypt yet only the recipient can decrypt it. No need to transfer secret keys

Cryptography - Making and breaking of secret codes Translation of the original message into a new incomprehensible one by a mathematical algorithm using a specific KEY Plaintext - a message or data Ciphertext - coded text Decryption - decoding back to plaintext

Encryption Includes: Coding scheme or cryptographic algorithm Specific sequence of characters key used by the algorithm

Examples Cereal box codes Substitute cipher Cryptoquip in newspaper

Variations - Symmetric Use the same key to encrypt and decrypt (secret key) Requires a more secure system to send the key than the system itself

Public Key Cryptography Public Keys –Secret key for each pair of parties who wish to communicate privately –key is passed between the parties in a method more secure than the method used for sending the messages

Variations - Asymmetric Use a key (public key) to encrypt a message Another (private key) to decrypt it Requires both keys

Reliability The longer the key has remained unbroken, the stronger it is likely to be The longer the key is in use, the more likely someone will be able to discover it –larger amount of info will be compromised –change key frequently

Available Algorithms DES – Data Encryption Standard RSA algorithm PGP – Pretty Good Privacy IDEA – International Data Encryption Algorithm Digital Signature

DES - Data Encryption Standard Developed by IBM Adopted as a Federal Information Processing Standard Uses a 56 bit key Has been broken To extend life - extend key to 128 bits –or triple DES

RSA algorithm Used in public key cryptography Patented in US Based on multiplication of large prime numbers

PGP - Pretty Good Privacy Based on RSA Used for protecting Free Distributed on Internet Developed by Zimmerman for use with E- Mail

IDEA - International Data Encryption Algorithm 1991 in Switzerland Uses bit key More mathematical theory than DES

Digital Signature Add a statement of acceptance to the electronic document –encrypted with private key –cyphertext is decrypted with public key –providing any other key produced gibberish Others can decrypt and read but only the one with the right key is signed