Block or Stream Cipher? — TechKnowSurge

About this interactive

Symmetric ciphers, where the same key encrypts and decrypts, do the bulk of the encrypting in the world, and they come in two kinds. The difference is simply how many bits the cipher processes at a time. A block cipher works through the data in fixed-size chunks. DES uses 64-bit blocks, which set a precedent many ciphers follow, and AES uses 128-bit blocks. If the last piece of data does not fill a block, the cipher has to add padding before it can encrypt it. Block ciphers are the more common kind and are generally easier to implement. DES, Triple DES, AES (the Rijndael cipher), RC5, Blowfish and Twofish are all block ciphers. A stream cipher encrypts a single digit at a time, usually one bit, sometimes one byte, as the data flows in or out. Because it only ever holds a tiny piece, it uses less memory and is more efficient. RC4 is the stream cipher to remember, and it is easy to mix up with RC5, which is a block cipher. One trap: do not sort by use case alone. A stream cipher suits streaming data, but a 64-bit block is small, so block ciphers are used for streams too. Ask how much data is processed at once.

What you'll learn

Distinguish a block cipher from a stream cipher by how much data it processes at a time, a fixed-size block or a single bit or byte
Identify DES, Triple DES, AES, Rijndael, RC5, Blowfish and Twofish as block ciphers and RC4 as a stream cipher, and recognize padding, memory use and efficiency as consequences of the difference

Aligned to

ISC2 CC

5.1 Understand data security

CompTIA Security+

1.4 Explain the importance of using appropriate cryptographic solutions.

Cisco CCST Cybersecurity

1.4 Explain encryption methods and applications

Key terms

Block Cipher: A symmetric cipher that encrypts data in fixed-size chunks called blocks, with the block size determined by the cipher and its settings.
Stream Cipher: A symmetric cipher that encrypts data one bit or byte at a time as it is transmitted, using less memory and offering greater efficiency than block ciphers.
Symmetric Encryption: An encryption method that uses the same key for both encryption and decryption.
Digital Encryption Standard: Digital Encryption Standard is a symmetric-key block cipher with a 56-bit key that was once the federal standard for encryption but is now considered cryptographically broken due to its small key size.
Triple Data Encryption Standard: Triple DES is a symmetric block cipher that applies the DES algorithm three times to each data block using two or three keys, providing stronger encryption than single DES but now considered deprecated due to slow speed and small block size.
Advanced Encryption Standard: A symmetric encryption algorithm widely used to secure data, supporting key sizes of 128, 192, and 256 bits.
Rivest Cipher 4: Rivest Cipher 4 is a stream cipher that was widely deployed in WEP, SSL, and TLS but is now considered cryptographically broken due to statistical biases and key scheduling weaknesses.

Topics

Interactive Streak Sort

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