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Definitions
Algoritm: The set of mathematical rules used in encryption and decryption.
Cryptography: Science of secret writing that enables you to store and transmit data in a form that is available only to the intended individuals.
Cryptosystem: Hardware or software implementation of cryptography that transforms a message to ciphertext and back to plaintext.
Cryptoanalysis: Practice of obtaining plaintext from ciphertext without a key or breaking the encryption.
Cryptology: The study of both cryptography and cryptoanalysis.
Ciphertext: Data in encrypted or unreadable format.
Encipher: Act of transforming data into an unreadable format.
Decipher: Act of transforming data into a readable format.
Key: Secret sequence of bits and instructions that governs the act of encryption and decryption.
Key clustering: Instance when two different keys generate the same ciphertext from the same plaintext.
Keyspace: Possible values used to construct keys.
Plaintext: Data in readable format, also referred to as cleartext.
Work factor: Estimated time, effort, and resources necessary to break a cryptosystem.
Types of ciphers
Substitution cipher: Replaces bits, characters, or blocks of characters with different bits, characters or blocks.
Transposition cipher: Permutation is used, meaning that letters are scrambled. The key determines the positions that the characters are moved to.
Frequency analysis: Analysis of the frequent patterns of letters used in messages and conversation.
Running key cipher: Uses steps in the physical world around us, like books (page, line number and word count). Each word is described by a sequence of numbers.
Concealment cipher: Every X number of words within a text, is a part of the real message.
Steganography: Hiding data in another message so that the very existence of the data is concealed. A message can by hidden in a wave file, in a graphic or in unused spaces on a hard drive or sectors that are marked as unusable.
Clipper chip: A NSA designed tamperproof chip for encrypting data. Uses the SkipJack algorithm. Each Clipper Chip has a unique serial number and a copy of the unit key is stored in the database under this serial number. The sending Clipper Chip generates and sends a Law Enforcement Access Field (LEAF) value included in the transmitted message. Based on a 80-bit key and a 16-bit checksum.
Key Escrow: The unit keys are split into two sections and are given to two different escrow agencies to maintain.
Fair cryptosystems: Separate the necessary key required for decryption, but this method takes place in software encryption processes using public key cryptography, whereas key escrow is mainly used when hardware encryption chips are used.
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