Use this tag for questions about cryptographic algorithms which were invented (and used) before the computer age.
1
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2answers
180 views
Kryptos : K1. What is the origin of the “palimpsest” keyword?
I'm studying the Kryptos sculpture with its cryptographic puzzles K1 to K4.
I understand that the keyword "palimpsest" was reverse-engineered using the tableau (and brute-force computer processing), ...
7
votes
4answers
483 views
Cracking WWII-era codes - code found on a pigeon's leg in Surrey
A recent BBC article entitled WWII code 'may never be cracked' posted a code:
AOAKN HVPKD FNFJW YIDDC
RQXSR DJHFP GOVFN MIAPX
PABUZ WYYNP CMPNW HJRZH
NLXKG MEMKK ONOIB AKEEQ
WAOTA RBQRH DJOFM TPZEH
...
2
votes
2answers
295 views
How to get the keyword from a keyword cipher?
I was given a ciphertext and now I am trying to break it via looking for the keyword.
This is a keyword cipher. So:
PlainEnglish: ABCDEFGHIJKLMNOPQRSTUVWXYZ
If ...
6
votes
1answer
368 views
How to deduce enigma settings given a partial plaintext?
Assuming some large block of text is encrypted with an enigma machine and I only know a small subset of letters before and after encryption, how do I go about figuring out the enigma settings from ...
5
votes
2answers
379 views
Using a mono-alphabetic substitution cipher with a different language per word
How much harder is it to determine the secret key for a mono-alphabetic substitution cipher, if each word is translated into a different language before the cipher is applied?
EDIT
If somehow ...
5
votes
2answers
855 views
How to attack a classical cipher using known partial plaintext?
I have a ciphertext generated by a classical cipher. I do not know what was cipher used to generate it. I do however have the beginning of the plaintext.
What are the cryptanalysis approaches for ...
3
votes
1answer
229 views
What is the best method to determine the language used in a monoalphabetic substitution cipher?
Working on a cipher (which I assume to be a mono-alphabetic substitution cipher due to the letter frequency) I struggle with the fact that I don't know which language the plain text is written in. ...
3
votes
3answers
372 views
Alphabetic Substitution with Symbols
I was reading on a site about the Zodiac Killer and how he used a basic substitution cipher, but instead of substituting english letters and characters he substituted symbols.
I was wondering, if you ...
7
votes
1answer
3k views
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) ...
12
votes
4answers
540 views
Can an Enigma-style cipher of sufficient complexity be considered secure in today's world?
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 ...
12
votes
2answers
791 views
What are the main weaknesses, if any, of a Playfair cipher?
What are the main weaknesses, if any, of a Playfair cipher?
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 ...
