Cryptography

• Cryptography

  The science of encryption, known as cryptology, encompasses cryptography and cryptanalysis
• Cryptography


  The process of making and using codes to secure the transmission of information
• Cryptanalysis


  The process of obtaining the original message (called the plaintext) from an encrypted message (called the ciphertext) without knowing the algorithms and keys used to perform the encryption
• Encryption


  The process of converting an original message into a form that is unreadable to unauthorized individuals
• Decryption


  The process of converting the ciphertext message back into plaintext so that it can be readily understood
• Algorithm


  The programmatic steps used to convert an unencrypted message into an encrypted sequence of bits that represent the message
• Cipher or cryptosystem

  An encryption method or process encompassing the algorithm, key(s) or cryptovariable(s), and procedures used to perform encryption and decryption
• Ciphertext or cryptogram


  The encoded message resulting from an encryption
• Code

  The process of converting components (words or phrases) of an unencrypted message into encrypted components
• Decipher


  To decrypt, decode, or convert, ciphertext into the equivalent plaintext
• Encipher

  To encrypt, encode, or convert, plaintext into the equivalent ciphertext
• Key or crypto-variable


  The information used in conjunction with an algorithm to create the ciphertext from the plaintext or derive the plaintext from the ciphertext
• Keyspace


  The entire range of values that can be used to construct an individual key
• Link encryption

  A series of encryptions and decryptions between a number of systems, wherein each system in a network decrypts the message sent to it and then reencrypts it using different keys and sends it to the next neighbor, and this process continues until the message reaches the final destination
• Plaintext or cleartext


  The original unencrypted message, or a message that has been successfully decrypted
• Steganography


  The hiding of messages—for example, within the digital encoding of a picture or graphic
• Work factor


  The amount of effort (usually in hours) required to perform cryptanalysis to decode an encrypted message when the key or algorithm (or both) are unknown
• Substitution Cipher

  1. Substitute one value for another, for example a letter in the alphabet with the letter three values to the right

  2. Substitute one bit for another bit that is four places to its left
• The Vigenere cipher is a plain-text form of encoding that uses alphabetical substitution to encode text. This ancient form of cryptography dates back to the 1400s and was documented in the works of famous writers of the era such as Trithemius.