6.2 Explain cryptography algorithms and their basic characteristics

polyalphabetic substitution cipher

A polyalphabetic substitution cipher is a substitution cipher using multiple alphabets, such as the 26 alphabets of the Vigenère cipher.

BCRYPT

Bcrypt is an example of a key-stretching technology. It's based on the Blowfish cipher, it uses salting, and it includes an adaptive function to increase iterations over time.

Blowfish and Twofish.

Bruce Schneier's Blowfish block cipher supports keys of 32-488 bits in length. The Twofish algorithm developed by Schneier, derived from Blowfish, was an AES finalist.

DSA

DSA (Digital Signature Standard) is a method for creating digital signatures and is a FIPS (Federal Information Processing Standard) (specifically FIPS 186).

DHE and ECDHE

Diffie-Hellman (D-H) Ephemeral (DHE, aka Ephemeral Diffie-Hellman [EDH]) is a variation of D-H that is used by TLS to implement perfect forward secrecy by performing multiple rekey operations in a session. Elliptic Curve Diffie Hellman Ephemeral, or Elliptic Curve Ephemeral Diffie-Hellman (ECDHE), implements perfect forward secrecy through the use of elliptic curve cryptography (ECC).

frequency analysis

Frequency analysis is the frequency occurrence of letters within a written language that are retained in the substitution cipher text.

PGP and GPG

PGP (Pretty Good Privacy) and GPG (GNU Privacy Guard) are email security products that can also be used to encrypt and digitally sign email messages. PGP uses proprietary certificates.

PBKDF2

Password-Based Key Derivation Function 2 (PBKDF2) is an example of a key-stretching technology. It uses a hashing operation, an encryption cipher function, or an HMAC operation (a symmetric key is used in the hashing process) on the input password, which is combined with a salt.

period analysis

Period analysis is an examination of frequency based on the repeated use of the key or secret that reveals a pattern of encryption.

RIPEMD

RIPEMD-160 is a 160-bit hashing algorithm that is a derivative of RACE (Research and Development in Advanced Communications Technologies in Europe) Integrity Primitives Evaluation Message Digest (RIPEMD), which was itself a variant of MD4.

ROT13

ROT13, or rotation 13, is a substitution cipher based on the 26 letters of the English alphabet (or the basic Latin alphabet). The operation of ROT13 is to shift or substitute each original plain text letter with the letter located in 13 positions further down the alphabet.

RC4

Rivest Cipher 4 (RC4) is a 128-bit stream cipher. It's the foundation of the WEP and WPA encryption used for wireless networking.

substitution ciphers

Substitution ciphers use the encryption algorithm to replace each character or bit of the plain text message with a different character. The Caesar cipher (C3) is a good example of a substitution cipher.

Advanced Encryption Standard (AES)

The Advanced Encryption Standard utilizes the Rijndael algorithm and is the U.S. government standard for the secure exchange of sensitive but unclassified data. AES uses key lengths and block sizes of 128, 192, and 256 bits to achieve a much higher level of security than that provided by the older DES algorithm.

basics of the Data Encryption Standard (DES) and Triple DES (3DES)

The Data Encryption Standard (DES) is a 64-bit block cipher that provides 56 bits of key strength. 3DES is a variation of DES that has an effective key strength of either 168 bits or 112 bits.

HMAC

The Hash-Based Message Authentication Code (HMAC) algorithm implements a partial digital signature—it guarantees the integrity of a message during transmission, but it doesn't provide for nonrepudiation.

XOR

XOR (eXclusive OR) is an exclusive disjunction, which means that it produces an output of truth (or 1) whenever the two inputs differ (such as one is a 0 [false] and the other is a 1 [true]).