Title: Cryptographic Algorithms
Course: IN 2001 Principle of Information Assurance > Section: Module 8: Chapter Eight

Cryptographic Algorithms
1. In general, cryptographic algorithms are often grouped into two broad categories: symmetric and asymmetric.
2. In practice, today’s popular cryptosystems use a hybrid combination of symmetric and asymmetric algorithms.
3. Symmetric and asymmetric algorithms can be distinguished by the types of keys they use for encryption and decryption operations.

Symmetric Encryption
1. Symmetric encryption uses the same key, also known as a secret key, to encrypt and decrypt a message.
2. Symmetric encryption methods can be extremely efficient, requiring minimal processing to either encrypt or decrypt the message.
3. The problem is that both the sender and the receiver must possess the encryption key.
4. If either copy of the key is compromised, an intermediate can decrypt and read the messages.
5. One of the challenges of symmetric key encryption is getting a copy of the key to the receiver, a process that must be conducted out-of-band to avoid interception.
6. Data Encryption Standard (DES)
  - The Data Encryption Standard (DES) was developed in 1977 by IBM and is based on the Data Encryption Algorithm (DEA)
  - As implemented, DES uses a 64-bit block size and a 56-bit key. With a 56-bit key, the algorithm has 256 possible keys to choose from (over 72 quadrillion)
  - DES is a federally approved standard for non-classified data
  - DES was finally cracked in 1997 when the RSA offered $10,000 as a reward to the team that could crack the algorithm
  - Fourteen thousand users collaborated over the Internet to break the encryption
7. Triple DES (3DES)
  - Triple DES (3DES) was developed as an improvement to DES. 3DES encrypts the message three times with three different keys
  - In 1998, it took a dedicated computer designed by the Electronic Freedom Frontier (www.eff.org) over 56 hours to break a DES key
8. The successor to 3DES is Advanced Encryption Standard (AES).
  - AES is based on the Rinjndael Block Cipher, a block cipher with a variable block length and a key length of either 128, 192, or 256 bits
  - It would take the same computer approximately 4,698,864 quintillion years to crack AES

Asymmetric Encryption
1. Asymmetric encryption is another category of encryption techniques also known as public-key encryption.
2. Symmetric encryption uses a single key to encrypt and decrypt.
3. Asymmetric encryption uses two different but related keys, one public and one private.  For example, if Key A is used to encrypt the message, only Key B can decrypt it.
4. The public key is stored in a public location where anyone can use it and the private key is known only to the owner of the key pair.

Encryption Key Size
1. When using ciphers, one of the decisions that has to be made is the size of the cryptovariable or key.
2. The strength of many encryption applications and cryptosystems is measured by key size.
3. When it comes to cryptosystems, the security of encrypted data is not dependent on keeping the encrypting algorithm secret; in fact, algorithms are often published so that research to uncover their weaknesses can be done.
4. The security of any cryptosystem depends on keeping some or all of the elements of the cryptovariable(s) or key(s) secret.