Solitaire is a low-tech encryption algorithm created by Bruce Schneier in 1999. It gained fame after being featured in Neal Stephenson’s book, Cryptonomicon. Similar to the One-Time Pad, Solitaire uses a deck of cards to encrypt and decrypt messages. The algorithm works by generating a pseudo-random keystream from a shuffled deck of cards. It has practical limitations, such as the need for a unique key for each message and the leakage of information at a rate of 0.0005 bits per character. However, Solitaire remains a secure and easily accessible encryption method.
https://alicegg.tech//2020/01/03/solitaire.html