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Questions tagged [cryptanalysis]

study of analyzing cryptographic systems in order to get information of the key or the message by finding weaknesses in the cryptographic algorithm.

The question on this tag should be related to one of the following subjects: Cryptanalysis methods, Cryptanalysis implementations. It should not contain question about: side channel attacks.

The quality of an attack is measured by 3 parameters:

  • Time: The amount of encryptions taken to attack. It can be splitted to time before attacking and online time.

  • Memory: Size of the needed memory.

  • Data: Amount of data needed to perform the attack. This can be known plaintext, chosen plaintexts, known ciphertext, etc.

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Should nonce / IV be private as a key?

In block cipher modes the nonce / iv and counters are introduced ( http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation). Should they also be private as a key and why?
good_evening
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generating 2^24 tables which differ only at one bit with c#

These days, I am working in the field of cryptanalysis and have started to do programming with C# Now, For finding the 5 optimal s-boxes(i mean those 2^24 tables), they should be generated, first.I know everything about the criteria for finding…
samsam114
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How to find RC4 key from decrypted and encrypted data?

I have some dump analysis in a documentation showing a bunch of encrypted data, and the resulting decrypted data. The algorithm used is explained (simple RC4). The only piece of information missing is the key used to get from the encrypted to the…
kriss
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How to distinguish between biased and random distributions

Actually, I am working on cryptography and I have to distinguish a number generated from a true random number generator and a number from a biased number generator. Is there any theorem to follow and know how many samples of data do we need to…
Cys
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Breaking Cipher text using frequency analysis / crypt analysis technique

How would you code a program ( preferably in Java or Python ) to break a random ciphertext where key can't be determined by shifts i.e the key substitution is random. This website (https://www.guballa.de/substitution-solver) has done it. I have to…
HAkid
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How we find a plaintext in rainbow table after delete all chain except first and end of chain

I started to learn rainbow tables and I have a question : How we can find a plaintext of hash if we delete all chain except first and end plaintext If It is wrong and we don't delete chain , why we don't use a normal pre-computing hashing…
Omar Bahy
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How to extract the keyword from a mono-alphabetic substitution cipher

I am a beginner to cryptography and i have the following the question. I know that to extract a plaintext from a mono-alphabetic substitution cipher i can perform shifting the characters by n times until i have the plaintext, or i can also use the…
john
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rainbow table integer representation of character string

I've been reading the documentation of RainbowCrack and older source code, and I can't locate where the developer(s) hash reduce to a 64-bit integer, which can hold UINT64_MAX plain texts. Doc:…
JYG
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Application with AES encryption - test

Im implementing the algorithm AES in my mobile app with a 128 bit key, now im wondering how to actually test if the encryption works and how secure is it, is there a way that i can simulate an attack to my application (maybe a free software)? so i…
Fernando Ojeda
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How can I write vigenere cryptanalysis of persian text?

How can I write Vigenere cryptanalysis for persian language? Is there any sample source code for persian?
viol
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How is it possible to break encrypted public key (RSA) using password as symmetric key?

Given public key (RSA) encrypted with symmetric key (password) and if password is weak, then how is it possible to find password using given encrypted public key only.
B Avinash
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Why DES is insecure? How do we know when to stop iterating and that we've found out the key?

It's said that DES is insecure. I guess it's because the key is 55 bit long, so using brute-force would take max 2^55 iterations to find out the key which is not many nowadays. But if we iterate 2^55, when do we know when to stop?
good_evening
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How to find the prime factors of a number with python

I'm writing a program that will calulate the private key for a weak RSA public key. I am wondering how I would go about determining the values for p and q from the value n. Here is the Python code so far: from Crypto.PublicKey import RSA…
Legorooj
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What flaws are exposed if encrypted version of plain message is always the same?

I am working on a small encryption program which takes in a message, such as "Hello there!". Whenever I run the program with a message it produces the same encrypted result "Hu8z209=yTu83tu8". If I approached breaking the encryption using…
tpm900
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