ITSY-1300 Chapter 8 - Cryptography

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

Monoalphabetic substitution

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 transmitted with the message so it can be compared with the recipient's locally calculated hash of the same message. If both hashes are identical after transmission, the message has arrived without modification. Also known as a hash value.

Substitution cipher

an encryption method in which one value is substituted for another.

Asymmetric encryption

an encryption 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.

Cryptography

the process of making and using codes to secure the transmission of 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.

Steganography

a data hiding method that involves embedding information within other files, such as digital pictures or other images.

Exclusive OR operation (XOR)

a function within Boolean algebra used as an 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.

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 3DES symmetric key encryption and RSA for key exchanges and digital signatures.

Polyalphabetic substitutions

a substitution cipher that incorporates two or more alphabets in the encryption process.

Transposition cipher

also known as a permutation cipher, an encryption method that involves simply rearranging the values within a block based on an established pattern to create the ciphertext.

Transport mode

an IPsec mode in which only the IP data is encrypted, not the IP headers.

Tunnel mode

an IPsec mode in which the entire IP packet is encrypted and then placed into the content portion of another IP packet.

Vigenère cipher

an advanced type of substitution cipher that uses a simple polyalphabetic code

Private-key encryption or symmetric encryption

an encryption method that incorporates mathematical operations involving the same secret key both to encipher and decipher the message.

Vernam cipher

an encryption process that generates a random substitution matrix between letters and numbers that is used only one time. Also called a one-time pad.

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 Infrastructure (PKI)

an integrated system of software, encryption methodologies, protocols, legal agreements, and third-party services that enables users to communicate securely through the use of digital certificates.

Internet Protocol Security (IPSec)

an open-source protocol framework for security development within the TCP/IP family of protocol standards

Digital signatures

encrypted message components that can be mathematically proven as authentic.

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.

Application header (AH) protocol

in IPsec, a protocol that provides system-to-system authentication and data integrity verification, but does not provide secrecy for the content of a network communication.

Certificate revocation list (CRL)

in PKI, a published list of revoked or terminated digital certificates.

Certificate authority (CA)

in PKI, a third party that manages users' digital certificates.

Registration authority (RA)

in PKI, a third party that operates under the trusted collaboration of the certificate authority and handles day-to-day certification functions.

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 algorithms

public functions that create a hash value, also known as a message digest, by converting variable-length messages into a single fixed-length value

Digital certificates

public-key container files that allow PKI system components and end users to validate a public key and identify its owner.

Public-key encryption

see asymmetric encryption.

Permutation cipher

see transposition cipher.

Digital Signature Standard (DSS)

the NIST standard for digital signature algorithm usage by federal information systems. DSS is based on a variant of the ElGamal 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.

Cryptology

the science of encryption, which encompasses cryptography and cryptanalysis.