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I enjoy making notes and passing them to my friends, and I also like making them encrypted for no reason. My friends enjoy it too, but it's a bit annoying to use the Caesar cipher for everything because its repetitive and takes forever. Is there a better pen-and-paper way of encrypting messages?

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  • $\begingroup$ takes forever? what do you want to do with pen-and-paper, parallel pen-and-paper computation? At the end, classical ciphers operates on characters and you have to deal with them one-by-one. $\endgroup$ – kelalaka Sep 23 at 6:53
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Yes, for the purpose of amusement you have better, more interesting ways to create and share a hand cipher.

A wide selection of defunct ciphers awaits you.

The Vigenère cipher might be interesting because encryption and decryption are easy, and you get to choose the word or words that will encrypt the plaintext.

You could use transposition alone as a hand cipher: the Rail Fence cipher (which can be quick), columnar transposition (single or double; broken transpostion or not), which uses keywords; or the Route cipher. Any of these will make most folks scratch their heads.

Or you could get more serious and imitate the VIC cipher, which the Soviets employed during the early Cold War.

In fact, you have a myriad of options--the ADFGVX cipher, which is a fractionating transposition cipher; simple substitution such as ROT13; a straddling checkerboard by itself, which fractionates the message (the straddling checkerboard is part of the VIC Cipher); employ a scrambled checkerboard; create a dictionary and use homophonic substitution the old-school way; create a code book and use code alone or as part of another system; or even generate keys in a truly random manner, share and store them securely, and create your own one-time pad (which is not defunct at all as a system in and of itself and can be quite fast for encryption and decryption).

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Most of the classical crypto algorithms used in the pre computer era can be doable with pen and paper!! Lot of there are in the list see here http://practicalcryptography.com/ciphers/classical-era/ . Try Vigenere and change you keys frequently.

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