Cryptography Stack Exchange
Cryptography Stack Exchange

Questions tagged [classical-cipher]

Ciphers invented before the era of computers and modern cryptographic theory. Classical ciphers typically operate on letters instead of bits and are usually designed to be implemented by hand or using simple mechanical devices.

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Possible ways to crack simple hand ciphers?

We had a quiz in class today where we had to break the ciphertext with the key given, but not the algorithm. Suffice to say that I wasn't able to decrypt it within the allotted time of 12 mins and will probably get a 0% score on the quiz. So, I was…
GamingX
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What is the most secure hand cipher?

By "hand cipher", I mean a symmetric cipher for which encryption and decryption can can both be performed with a pencil on graph paper, consuming about 10-20 seconds per character by a proficient user. Additional simple tools, e.g. a deck of cards…
Jordan
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What are the main weaknesses of a Playfair cipher, if any?

What are the main weaknesses of a Playfair cipher, if any? I know that they depend on none of the letters missing, but that is an easy fix if a letter gets dropped. Besides that, are there any other problems with it?
Arlen Beiler
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Can an Enigma-style cipher of sufficient complexity be considered secure today?

Regarding the German Enigma machines, if I recall correctly, the reason they were defeated was because the Allies were able to generate a massive database of possible rotor settings, and because the day key was encoded twice in the beginning of each…
user93
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How were one-time pads and keys historically generated?

In the 20th century, it was common for various intelligence agencies and military organizations to use ciphering machines and one-time pads. However, no source I've seen ever mentions the process of generating the keys and printouts for such…
Mark
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Encryption/ciphers/codes in Chinese

I am quite curious as to how you can perform simple encryption for the Chinese language. Saw a similar question related to encryption/Chinese here: About cryptography in a character language, however the method of encryption appears to be quite…
pyko
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About Cryptography in a Character Language

Suppose I had a message in Chinese (or another non-phonetic language) and I wanted to encipher it. Some of the simplest encryptions in English are substitution ciphers, but such ciphers don't seem to be a viable option for a language such as…
davidlowryduda
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Which is the simplest cryptographic algorithm which is close to commercial-level security?

An algorithm is simpler than another if It is easier to explain to a noob with basic high-school math knowledge. It is easier to securely self-implement by an intermediate programmer (Yes I know one should never 'roll their own' but this is just a…
An Ant
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Creating your own encryption and decryption algorithm

I'm very uneducated when it comes to cryptography. I have tried to find an answer to my question, but what I've read doesn't quite cover what I'm asking. I have thought up my own encryption algorithm (which I'm sure is nothing new) and I would like…
user1575550
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How to build an electro-mechanical public key cipher machine?

It is generally assumed that asymmetric encryption schemes were invented in 1973 at GCHQ in Britain and, independently, in 1976 at the MIT. Imagine, if the abstract idea of having a public key and a private key that can only decrypt what has been…
Manuel Ebert
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Is the Caesar cipher really a cipher?

In this lecture by Dan Boneh on Coursera it was stated at minute 03:37 that The Caesar cipher, actually, is not a cipher at all. And the reason is that it doesn't have a key. What a Caesar cipher is, is basically a substitution cipher where the…
Pichi Wuana
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How does the index of coincidence work in the Kasiki test?

I'm starting to learn about cryptanalysis and I am having a bit of difficulty understanding the Kasiski test's index of coincidence. I have a book (Cryptography Theory And Practice by Douglas Stinson) about it that I'm going through, but it seems to…
norman
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Common Classical Ciphers

When studying cryptography, the first thing every student learns is some historical ciphers. There are way too many of those ciphers to name them all. So my question is: What are the most important classical ciphers (every cryptographer should have…
Titanlord
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How many keys does the Playfair Cipher have?

I was just studying the Playfair cipher and from what I've understood, it is just a slightly better version of a Caesar cipher, in that it isn't actually mono-alphabetic but rather the 'digrams' are mono-alphabetic. I believe that since it offers a…
GamingX
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Why was the Navajo code not broken by the Japanese in WWII?

In reading about this topic recently, to my understanding, the encryption schemes used on top of the Navajo language were very simple and definitely could have been broken (my research shows they mapped Navajo words to various different…
Michael Goldstein
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