# Tag Info

## Hot answers tagged substitution-cipher

Accepted

### Why is the Keyspace of a Substitution Cipher not 2^26 but 2^88

The key space of a cryptographic algorithm whose key length is $n$ is given by $2^n$ No. There is confusion between: keyspace (or key space) $\mathcal K$, which is the set of possible keys. keyspace ...
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### Is the Caesar cipher really a cipher?

He is talking about the original version of the Caesar Cipher where the substitution was just a +3: ...
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### Was the Enigma's double stepping mechanism intentional?

I suspect it was a semi-deliberate feature. That is, while it probably wasn't a design goal in and of itself, it neatly solved a mechanical issue that would otherwise have required a more complicated ...
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### Why is the Keyspace of a Substitution Cipher not 2^26 but 2^88

In the substitution cipher, the answer lies in the permutations, a key is one of the all possible permutations of the alphabet (keyspace), i.e. each letter is substituted with another. Therefore, for ...
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### In English, are there any words which encrypt to other words under the Caesar Cipher?

Actually, we have a four-way (that is, four words that will can be converted into any of the others with the right shift). These words are: ax, by, he, if Other ...
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### Does Format Preserving Encryption have significant advantages over a randomly generated lookup table?

any other considerations? Yes. In many common use cases the mapping table needs to be retained. That map changes each time a number is added; that's a backup / continuity of service headache. The ...
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### modified substitution permutation networks

Your construction is completely insecure: a single known plaintext / ciphertext block pair is sufficient to decrypt all blocks encrypted with the same key. Specifically, let me write your block ...
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### How were codes in WW1 reciphered (to enhance security levels) without them turning meaningless?

The concept is called superencipherment or multiple encryption, and works as follows: The original message M is enciphered using the code book, resulting in an enciphered message C1. C1 is then ...
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### Which sub operation is more expensive in the AES encryption process?

The table lookup implementations usually combine the SubBytes and ShiftRows steps with the MixColumns step. Different implementations/hardware/etc make general statements impossible, but this paper ...
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### How to break homophonic substitutions and nomenclators with too many symbols?

Regarding the first part of the question, I will just link to another answer I wrote in the past: Why don't homophones hide multiple-letter patterns? Summary: If you adjust the frequencies so that ...
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### How to encrypt this using caesar cipher?

The formula reads: C: ciphertext of a character E(P): encryption using Caesar of plaintext character = (Pi + 3) mod 26: index of character in alphabet, plus 3 (the key) and then modulus 26, the size ...
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### Not-So-Simple Substitution Cipher?

This is called homophonic encryption, and has been around for a long time. In terms of cryptanalysis of such ciphers, there is a nice thesis from SJSU on this topic which is available here. The ...
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### Does composing multiple substitution ciphers improve security?

I don't have enough space to expand on yyyyyyy's answer in a comment so I am making this an answer in and of itself. TruthSerum is correct, but it seems like an explanation is wanted, so here goes. ...
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### Which cipher text is easiest to guess the plaintext?

You're right. For a substitution cipher the huge size of the keyspace is quite irrelevant in terms of security: it does not change the frequencies of letters, just maps them to other letters. So you ...
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### How to distinguish a transposition cipher from a simple substitution cipher only given a ciphertext?

Think about what properties of the plaintext are preserved by the candidate ciphers. You want to look for those patterns. Transposition moves letters around but keeps their identity. Substituting ...
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### Why is the Keyspace of a Substitution Cipher not 2^26 but 2^88

The key of your misunderstanding is the following sentence: Assuming the key length is 26 The conceptual mistake you made is that you forgot the unit: Does "26" mean "26 bits", "26 decimal digits"...

### How were codes in WW1 reciphered (to enhance security levels) without them turning meaningless?

Anyone could be confused by this, especially by the part about the Zimmermann telegram. Codebooks come in three flavors: one-part, two-part, and hybrid. You described a one-part codebook. These are ...
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### How do AES Substitution box's offer any additional security since it's 1 to 1?

Philosophically any invertible cipher (it would be useless if not invertible) is just a one to one map, so no cipher would be secure under your argument. Specifically, the Sbox has been carefully ...
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### How does the ring settings of enigma change wiring tables?

Ok, here we go. Let's use Rotor I as an example. The wiring for this rotor looks like this: EKMFLGDQVZNTOWYHXUSPAIBRCJ On every rotor, there originally was a ...
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### Frequency analysis

My answer won't please you but we don't analyze cipher here. Your design is interesting in term of pen and paper, but might still be sensible to statistical analysis given a long enough cipher text. ...
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### How to break a Quagmire 3 cipher?

All the Quagmire ciphers (see e.g. here for definitions) are combinations of a VigenĂ¨re shift cipher and a keyword-based simple substitution cipher, where the substitution cipher is used to scramble ...
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### I have a encryption png file

The reason your code doesn't work is that you haven't figured out how to decrypt the byte values that don't appear in the header or in the final sequence. While you could try to break this encryption ...
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### Mathematical structure for Sbox

Well, at least two representations come to my mind, but I'm afraid you will not find them too useful. In general, S-boxes are designed with the goal in mind that such "mathematical" representations do ...
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### In English, are there any words which encrypt to other words under the Caesar Cipher?

The longest pairs 1 (and 25): Common: Steeds and Tuffet Uncommon: Anteed and Bouffe (If you paid your ante, you anteed, bouffe is another word for bouffant, a type of hat) 2 (and 24): Common: ...
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