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Questions tagged [vigenere]

The Vigenère cipher is a classical cipher that shifts each plaintext character by the value of the key at the same position modulo the key-length.

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Conditions for Perfect Secrecy with the Vigenere Cipher

Please forgive my ignorance here as I'm far from a math major and I've never looked into cryptography before so if this seems stupid - it probably is. There is a question in a quiz I'm attempting that is just doing my head in. If you are wondering -…
Chris
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Vigenère ciphertext encrypted with another Vigenère cipher

I have been learning about Vigenère ciphers and then thought of this scenario: A cryptographer encrypts a plaintext English message with a Vigenère cipher, then another cryptographer, who wants to ensure that the message is very secure, encrypts…
Jok3r
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Is Vigenere's cipher really breakable for very long cipher keys?

It is argued that the Vigenere cipher is easy to break using the Babbage's solution. But this solution counts on finding the repetetive occurences of letter groups(words if you will). What if my key is thousand letters long. Wouldn't it then be very…
Giray Sekerlen
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How to crack Vigenere ciphertext if multiple keys of coprime length are used?

I came across the idea of using multiple Vigenere keys of coprime lengths here. The idea is, what if you use multiple keys, whose lengths are all co-prime? Then your effective key length would be the product of the length of all keys since they…
Meler Lawler
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Is the beaufort cipher just as secure as the Vigenere cipher?

Does the Beaufort cipher have the same strength as the vigenere cipher assuming you use the same complexity of key, or because of it's reciprocal nature make it less secure?
Cody
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Vigenère cipher

I am attending a cryptography course on Coursera. I am stuck at one question which I cannot answer right, even after a few tries. Which of the following are true about Vigenère cipher? (Check all that apply) A Vigenère cipher with key of length…
Daniela
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Probability of Vigenere cipher

I am trying to figure out this quiz question on a course I am doing but keep getting it wrong. Consider the Vigenere cipher over the lowercase English alphabet, where the key can have length 1 or length 2, each with 50% probability. Say the…
Lilz
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Question about variations on Vigenere cipher

I'm new here and by no means an expert on cryptography. I like to dabble, and one of my favorite classical ciphers is the Vigenere. I understand that the normal method of Vigenere encrypting is to add the corresponding number of the letter of the…
Douglas Harbert
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Attacking a variation of the Vigenere with very long key length

I am to decrypt the ciphertext YVBCXGJRYHHRCJIUL into its plaintext message. The information that I am given is that the key used in the cipher is very long (equivalent to the length of an entire book) and that the key is certainly longer than the…
Slippy
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How to find key length of a Vigenere chiper?

I am trying to decrypt a Vigenere chiper, I saw a lot of youtube videos but I still can get a good value for the key length. In theory I have to get the repetions of letters shifting the text one place every iteration and then see how many steps…
Roger Coll
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Base 64 Vigenere

I'm working on breaking a base64 Vigenere cipher. My guess is that the plaintext has been first base64-encoded, and then a variation of Vigenere with a 64*64 alphabet table used, the alphabet being composed of abc..xyzABC..XYZ012..789/+" The cipher…
Amber
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Probability for Vigenere cipher given distribution of key lengths

Given the exact same question and answer here: https://crypto.stackexchange.com/a/37212/40935. How does one derive/figure out (using equation, combination of equations, or "knowledge") the bold marked parts in the following: How does one know to…
Henrik
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Conditional probability with Vigenere Cipher given specific plaintexts and key sizes

Apologies if this should be in the Mathematics stack exchange, I just ask it here because the context is cryptography. Here is the question that I seemingly cannot get correct: Consider the Vigenere cipher over the lowercase English alphabet, …
Chris
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Cracking vigenere of non-text cleartext

I've begun a course in crypto on coursera and the first homework was writing a vigenere(xor) cracker. It works, which was a rush :) but it makes one core assumption, one has encrypted a natural language text that the script can use frequency…
dutt
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Encipher the following plaintext message using the Vignere method using the key K = [4,2,3]

Encipher the following plaintext message, Exotic, using the Vignere method using the key K = [4,2,3] Can anyone help me get the answer and why, can't find anything that matches this question online.
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