Vernam Cipher

Vernam Cipher is a #Substitution Cryptographic #algorithm invented by Gilbert Vernam in 1918. It works on the binary data with bit-wise XOR operation (or in Modular Arithmetic, $\mod 2$) and chooses a key with no statistical relationship with the plaintext. It is widely adopted as it could be implemented easily using hardware circuits. The encryption scheme is formalised using the following equations:

$$ \begin{align} C &= E_k(P) = P \oplus K\\ D &= D_k(C) = C \oplus K\\ \end{align} $$

Where:

$C$ is the ciphertext
$P$ is the plaintext
$K$ is the key
$E$ is the encryption algorithm
$D$ is the decryption algorithm

Links to this page

TAC3121 Chapter 3: Classic Ciphers

Vernam Cipher
Substitution Cryptography

Vernam Cipher#
One-Time Pad

One-Time Pad, or sometimes called One-Time Vernam Cipher#, is a #Substitution Cryptographic #algorithm that uses a single-use secret key for encrypting. It requires the key to be as long as the plaintext and random. Thus, guarantees an Unconditional Security# to the ciphertext. However, it does face some security concerns over secure key distribution and key generation for randomness. It is only used for low bandwidth and very high security purposes.