Encryption Flashcards
(16 cards)
Substitution Algorithm
A substitution cipher replaces each character in plaintext with another character based on a fixed system, like shifting the alphabet by 3 spaces.
Transposition Algorithm
In a transposition algorithm, the letters stay the same, however their order may change places in complex fashions.
Symmetric algorithm
A symmetric algorithm is one in which encryption and decryption are both performed by the same secret key.
Symmetric encryption
Two-way encryption scheme in which encryption and decryption are both performed by the same key. Also known as shared-key encryption.
The most common symmetric algorithm is the Advanced Encryption Standard (AES), also known as the Rijndael cipher. Other common symmetric algorithms include Data Encryption Standard (DES), Rivest’s Cipher (RC), International Data Encryption Algorithm (IDEA), Blowfish, Twofish, and CAST.
Advanced Encryption Standard (AES)
The most common symmetric algorithm is the Advanced Encryption Standard (AES), also known as the Rijndael cipher. It was developed by Jaon Daemen and Vincent Rijmen in 2001 as part of a NIST competition held to find a replacement for DES. AES offers three different key lengths of 128, 192, and 256 bits. AES is used in many applications, including 802.11 communications, Bitlocker, and game engines.
Keyspace
The range of values that the key can be in.
Key Length
The number of bits used for the key.
Asymmetric Algorithms
With an asymmetric algorithm , encryption and decryption are performed by two different but related public and private keys in a key pair.
Public Key
During asymmetric encryption, this key is freely distributed and can be used to perform the reverse encryption or decryption operation of the linked private key in the pair.
Private Key
In asymmetric encryption, the private key is known only to the holder and is linked to, but not derivable from, a public key distributed to those with whom the holder wants to communicate securely. A private key can be used to encrypt data that can be decrypted by the linked public key or vice versa.
Rivest-Shamir-Adleman (RSA)
Asymmetric Algorithm
RSA was developed by Ron Rivest, Adi Shamir, and Leonard Adleman. RSA was released shortly after Diffie-Hellman in 1977.
RSA is still one of the most commonly used algorithms and helped define the process of using a public key to encrypt data and a private key to decrypt the data.
RSA is used extensively for creating digital signatures.
Elliptic Curve Cryptography (ECC)
Asymmetric Algorithm
Elliptic Curve Cryptology is one of the newer methods being implemented. It was originally introduced in 1985. It did not enter wide usage until 2004.
ECC is able to generate smaller keys that are more secure than most other methods.
Many websites today use ECC to secure connections and data transmissions.
Diffie-Hellman
Asymmetric Algorithm
Released in 1976 by Whitfield Diffie and Martin Hellman. Its purpose was to allow two users who have never met to safely create a shared key over a public channel such as the internet.
Diffie-Hellman is frequently implemented in security protocols such as TLS, IPSec, SSH, and others.
Digital Signature Algorithm (DSA)
Asymmetric Algorithm
DSA was proposed in 1991 by NIST and became the government standard in 1993.
DSA is only used for creating digital signatures.
It uses a different algorithm than RSA but provides the same level of security.
Hybrid Cryptosystems
Hybrid cryptosystems combine the efficiency of symmetric encryption with the convenience of asymmetric encryption. A hybrid cryptosystem is used as follows:
User1 uses their symmetric private key to encrypt some data.
User1 then encrypts that symmetric private key using the recipient’s public key and sends both to the recipient.
User2, the recipient, uses their private key to decrypt User 1’s private key, which is then used to decrypt the message.
As long as User2’s private key is kept secret, the data remains secure.
Hybrid cryptosystems are used with many secure communication methods today, such as TLS.
Ephemeral Keys
In traditional encrypted communications, static keys are used. Ephemeral keys are generated for each new session or message sent. For example, perfect forward secrecy (PFC) uses ephemeral keys.
