Chapter 8 Cryptography
Symmetric Encryption
A cryptographic method in which the same algorithm and secret key are used both to encipher and decipher the message.
Asymmetric Encryption
A cryptographic method that incorporates mathematical operations involving both a public key and a private key to encipher or decipher a message. Either key can be used to encrypt a message, but then the other key is required to decrypt it.
Transposition Cipher
A cryptographic operation that involves simply rearranging the value within a block based on a n established pattern.
Vernam Cipher
A cryptographic technique developed at AT&T and knows as the "one-time pad" this cipher uses a set of characters for encryption operations only one time and then discards it.
Exclusive OR operation (XOR)
A function within Boolean algebra used as a encryption function in which two bits are compared. If the two bits are identical, the result is a binary 0; otherwise the result is a binary 1.
Diffie-Hellman Key Exchange
A hybrid cryptosystem that facilitates exchanging private keys using public-key encryption.
Secret Key
A key that can be used in symmetric encryption both to encipher and decipher the message.
message authentication code (MAC)
A key-dependent, one-way hash function that allows only specific recipients (symmetric key holders) to access the message digest.
Secure Electronic Transactions (SET)
A protocol developed by credit card companies to protect against electronic payment fraud.
Secure Sockets Layer (SSL)
A security protocol developed by Netscape to use public-key encryption to secure a channel over the internet.
Secure Multipurpose Internet Mail Extensions (S/MIME)
A security protocol that builds on the encoding format of the Multipurpose internet Mail Extensions (MIME) protocol and uses digital signatures based on public-key cryptosystems to secure e-mail.
Secure Hash Standard (SHS)
A standard issued by the National Institute of Standards and Technology (NIST) that specifies secure algorithms, such as SHA-1, for computing a condensed representation of a message or data file.
Privacy-Enhanced Mail (PEM)
A standard proposed by the internet engineering task force (IETF) that uses 2DES symmetric key encryption and RSA for key exchanges and digital signatures.
Polyalphabetic Substitution
A substitution cipher that incorporates two or more alphabets in the encryption process.
Monoalphabetic Substiution
A substitution cipher that only incorporates a single alphabet in the encryption process.
Message digest
A value representing the application of a hash algorithm on a message that is of the same message. If both hashes are identical after transmission, the message has arrived without modification. Also known as a hash value.
Vigenere Cipher
An advanced type of substitution cipher that uses a simple polyalphabetic code.
Substitution Cipher
An encryption method in which one value is substituted for another.
Secure HTTP (S-HTTP)
An extended version of Hypertext Transfer Protocol that provides for the encryption of protected Web pages transmitted via the internet between a client and server.
Public-key Encryption
Asymmetric encryption
Digital Signatures
Encrypted message components that can be mathematically proven as authentic.
Application Header (AH) Protocol
In IPSEC, a protocol that provides system-to-system authentication and data integrity but does not provide secrecy for the content of a network communication.
Encapsulating Security Payload (ESP) Protocol
In IPSec, a protocol that provides secrecy for the contents of network communications as well as system-to-system authentication and data integrity verification.
Tunnel Mode
In IPSec, an encryption method in which the entire IP packet is encrypted and inserted as the payload in another iP packet. This requires other systems at the beginning and end of the tunnel to act as proxies to send and receive the encrypted packets and then transmit the packets to their ultimate destination.
Transport Mode
In IPsec, an encryption method in which only a packet's IP data is encrypted, not the IP headers themselves; this method allows intermediate nodes to read the source and destination addresses.
Session Keys
Limited-use symmetric keys for temporary communications during an online session.
Hash functions
Mathematical algorithms that generate a message summary or digest (sometimes called a fingerprint) to confirm message identity and integrity.
Hash value
Message digest.
Hash algorithm
Public functions that create a hash value, also known as a message digest, by converting variable-length messages into a single fixed-length value.
Private-key encryption
Symmetric encryption
Digital Signature Standard (DSS)
The NIST standard for digital signature algorithm usage by federal information systems. DSS is based on a variant of the EIGamal signature scheme.
Advanced Encryption Standard (AES)
The current federal standard for the encryption of data, as specified by NIST. AES is based on the Rijndael algorithm, which was developed by Vincent Rijmen and Joan Daemen.
Cryptoology
The field of science that encompasses cryptography and cryptanalysis.
IP Security (IPsec)
The primary and now dominant cryptographic authentication and encryption product of the IETF's IP Protocol Security Working Group. A framework for security development within the TCP/IP family of protocol standards, IPSec provides application support for all uses within TCP/IP, including virtual private networks.
Steganography
The process of hiding messages; for example, hiding a message within the digital encoding of a picture or graphic so that it is almost impossible to detect that the hidden message even exists.
Cryptography
The process of making a and using codes to secure information.
Cryptanalysis
The process of obtaining the plaintext message from a ciphertext message without knowing the keys used to perform the encryption.
Nonrepudiation
The process of reversing public-key encryption to verify that a message was sent by the sender and thus cannot be refuted.
Permutation Cipher
Transposition Cipher