# 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.

237 questions
Filter by
Sorted by
Tagged with
50 views

### For fun puzzle has me stumped on a book cipher [closed]

So originally a puzzle was given out to a community i'm a part of and what was given was this. . .. . ... . . . . . . . ... . .. . . . . . .. . ... . . . . . .... . .. . . . . . .. .. .. . . . . . .. ....
83 views

### Interesting and fun facts about cryptology [closed]

We are planning to organize a workshop with the participation of academicians, engineers and graduate students working in the field of cryptology. On the first day, we are planning a fun competition ...
• 538
1 vote
42 views

### Could this be a cipher or not? [closed]

I am trying to solve a puzzle, and I think have to solve a cipher. But I'm not actually sure what I have to do ... Example : ...
• 11
1 vote
93 views

### How to Calculate Digraphic/Trigraphic Index of Coincidence?

How do you calculate the digraphic and trigraphic IOCs and the same expected IOCs? I'm aware of the formula for calculating the single letter IOC which is given at this formula but I can't find the ...
• 11
1 vote
136 views

### How do the notch and window positions on an Enigma machine correlate?

I am having difficulty visualizing the stepping process. The permutation of Wheel I of Enigma I is as follows: ...
342 views

### Keyless cipher proof

I answered a question on StackOverflow yesterday that was asking why the following keyless encoding/decoding scheme for 16-bit numbers worked: Encoding Note that the "shift" operation is ...
• 123
1 vote
33 views

### Is there any known/standard encoding or cipher method that uses a 64-character alphabet from byte 30 (ASCII 0) to byte 6F (ASCII o)?

Is there any known/standard encoding or cipher method that uses a 64-character alphabet from byte 30 (ASCII 0) to byte 6F (ASCII ...
• 111
156 views

### How do different types of ciphers relate to each other?

I understand that there are symmetric and asymmetric (public-key) cyphers. The first have the same key used for encryption and decryption, while the second use a public key for encryption and a ...
• 131
381 views

### Mathematical definition of scytale

Most cryptographers know the scytale. It is that cipher where you roll a leather strip around a rod and then write text on it. For encryption you roll it off the stick and for decryption you roll it ...
• 2,120
218 views

### Shift cypher, perfectly secure?

I know that if only one character is encrypted using a shift cipher, then the shift cipher is perfectly secure. But what if the space of keys is greater than the space of messages? Would it still be ...
• 23
1 vote
216 views

### Analysis of the Vigenere cipher

Im just starting out learning some cryptoanalysis techniques. I came across an idea which analyzes the vigenere cipher. Essentially the video explains that there is a standard english probability ...
59 views

### Using ML to detect what classical cipher the ciphertext is encrypted with

I was considering creating an ML project where it is fed some ciphertext by any classical cipher and would return possible ciphers that encrypted the text. I would have to create a sizeable dataset ...
• 21
166 views

### Does machine cryptography only consist of rotor machines?

For the chronological categorisation of cryptography, I have proceeded as follows: Cryptography by hand (e.g. Caesar, Vigenére, etc., till around 1900/1920) Cryptography using machines (e.g. Enigma, ...
• 2,120
74 views

### How to encrypt affine cipher in block?

Assuming the alphabet of capital letters, if an affine linear cipher $v\to Av+b \bmod 26$ with block length $3$ maps plaintext ENCRYPTAGAIN to ciphertext ...
154 views

### How are the cipher, the key and the initial message (that is not encrypted) are releted?

Suppose that $m$ is a message that someone player $i$ wants to send to a network of other players $j\neq -i$. The player to prevent his message from cheating by others uses an encyrpstion scheme. Say \$...
• 137
1 vote
294 views

• 1,000
1 vote
36 views

### Classic cipher method [closed]

I am struggling with these two cipher texts, I cannot identify which king of cipher was used. First: otnpeetrnneepeufofutisrtrllohcdmetoeheeatyngonrmrm And second: ...
114 views

### Running Key Gibbs Sampling

I am trying to implement the algorithm described in this paper. It uses blocked Gibbs sampling to perform a ciphertext-only attack on text encrypted with a running key cipher. However, I am confused ...
• 21
646 views

### Is it possible to crack the trifid cipher without the keyword?

I was learning about the classical ciphers and was looking up the methods to break them without the keywords and when I searched up "cryptanalysis of the trifid cipher" I couldn't find anything. I ...
1 vote
182 views

### Concatenating "words," is it possible to create a key that is indistinguishable from one made in a truly random manner?

By concatenating "words" and adding them Modulo 26, can a key be created that is indistinguishable from one generated in a truly random manner? Let's say the key is more than about ten ...
• 3,102