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A cipher is a process that obscures a message and encodes it, making the message obscured and not
understandable if intercepted. The intended recipient of the message then decodes it which then
reveals the message. (1)
A character cipher replaces one character with another. They're simple to use but rela vely easy to
crack. For example, with any reasonably large message, you can count the le#ers in the ciphertext
and guess the subs tu on using frequency tables for le#ers in the English language. (1) The
symbols are passed in plaintext. Character ciphers are not used in modern cryptography as they are
easy to solve.
Block ciphers group a predetermined count of characters into a block, and then encode the en re
block. A common vector is shared to encode and decode the block of characters. Most messages
using this method have to be padded at the end of the message so that the )nal block meets the
length requirements. Block ciphers are typically used in )le transfers and email transmissions, and
just about anywhere in cyber security. (2)
Stream ciphers use a common key to encrypt and decrypt plaintext data, similar to a block cipher.
However, a stream cipher encodes one byte of data at a me and uses a pseudorandom key string of
cipher digits when encryp ng. The opera on is very fast as it is performed at the byte level, using an
Exclusive-Or (XOR) calcula on. (3) Stream ciphers are used in SSL/TLS, Bluetooth, and Cellular and
4G connec ons. (2)
1. Bruce Ikenaga. No Date. Character Ciphers and Block
Ciphers. https://sites.millersville.edu/bikenaga/number-theory/character-
2. Hashed out, by the SSL store. January 14, 2021. Block Cipher vs Stream Cipher: What They
Are & How They Work. h#ps://www.thesslstore.com/blog/block-cipher-vs-stream-cipher/
3. Malviya, Nitesh. January 11, 2021. Understanding stream ciphers in cryptography.
h#ps://resources.infosecins tute.com/topic/stream-ciphers/
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