cryptography-otp.html
* created: 2025-10-06T19:26
* modified: 2025-10-27T15:23
title
One Time Pad
description
Description
related notes
One Time Pad (OTP)
The one type pad method uses a random key, which has to be as long as the message to be encrypted. The encryption part is just XOR.
- Encryption: M=D_{K}(C)=C \oplus K
- Decryption: C=E_{K}(M)=M \oplus K
Manipulating the cipher
If a bit shifts in the cipher text, the same bit in the message, which makes it possible to manipulate the message (secrecy but not integrity).
Can't use the same key twice.
C \oplus C' = M \oplus M'