# Tagged Questions

Cryptographic functions which transform plaintext into ciphertext or the other way around.

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### A software for test and performance analysis of cryptographic algorithms

I'm new to cryptography and I have been assigned at college to do a comparison study between AES, DES, RC6 and SERPENT ciphers. Is there any graphical software than can help me analyze speed and ...
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### I've been sent a code in binary, but I can't seem to figure out what to do with it [closed]

My friend sent me a "puzzle" in binary, and said that there are multiple steps to solving the puzzle, all of them including decryption. I translated the binary into text and he said that was a good ...
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### prepaid meters that rely on a disconnected system

i have some experience with cryptography in the banking sectors, mostly in block ciphers like DES 3DES etc. im interested in prepaid electricity meters as it is a number that is generated from a ...
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### Is the “Matryoshka Cipher” possible to write and implement?

Named after the Russian nesting dolls (a physical representation of the hidden data and the layers of encryption surrounding it) one example of the Matryoshka cipher would be the "Zvyozdochkin set" ...
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### What is the main difference between a key, an IV and a nonce?

What are the main differences between a nonce, a key and an IV? Without any doubt the key should be kept secret. But what about the nonce and the IV? What's the main difference between them and their ...
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### Why are there no OTP ciphers?

We all know the OTP is unbreakable and we all love the OTP (judging by the amount of question on this site). The strength of the OTP is not that it is unable to find a word without the key but you ...
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### Why must the sender and receiver be synchronised in synchronous stream ciphers?

I would like to know why the sender and receiver must be synchronized in synchronous stream ciphers as said in Synchronous stream cipher. Why is there no synchronization between the sender and ...
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### Words in Index of coincidence using vignere

I am trying to interpret the formula for index of coincidence from here I am not understanding fi , How i can calculate fi in this context ? Is this the appearance of single word like (...
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### Finding Vignere Cipher key [closed]

I am new to cryptography and I am just trying to find key for random text. Can please explain the easy way how we can find the key in small number of steps ? if we have text like Peit Wokm! Mhfa ...
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### Would a pictographic, phoneme-based, hand cipher be difficult to crack with computer crypt-analysis?

What I'm talking about is a hand cipher which uses phonemes instead of individual characters and pictograms instead of the usual shuffling/substitution methods (e.g Caesar, Solitare, Vignere). The ...
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### Difference between the TLS cipher suites?

TLS_DHE_DSS_AES256_CBC_MAC / TLS_DHE_RSA_AES256_CBC_MAC Hi, I have been studying to learn about various cipher suites and their performances. I gathered that DSS is efficient when compared with RSA. ...
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### How do you implement a cipher as one lookup table?

I am reading up on whitebox cryptography and have trouble understanding how are ciphers implemented as one lookup table? assuming my plaintext is just 4 bits so the size of my lookup table should be ...
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### Creating a new cipher! [closed]

http://flashbackcipher.blogspot.ae/2015/03/introducing-flashback.html Hey guys the above is the blog for a new cipher, if you guys can take a look and suggest problems.. it would be of great help!! ...
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### What is the most light-weight symmetric cipher thats still usefull?

I need a very light encryption scheme which costs almost no performance during encryption (while decryption may be slow). I found 5 algorithms: RC4, DES, LED, PRESENT, and Piccolo. But how do I ...
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### Deciphering text encrypted with a changing cipher

I know there are many ways to crack basic ciphers were each letter is mapped to some other letter, but what ways are there to decode something that was encrypted using a cipher that changed after ...
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### When is a cipher considered broken?

We've all read how some people claim AES is broken because there was supposedly a way to get the plain text from a cipher text faster than brute-force. But is this the definition? Is a cipher broken ...
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### The exact difference between a permutation and a substitution

I've noticed confusing definitions about permutation and substitution, preventing to make the difference. A permutation changes the order of distincts elements of a set, but this can be writen as a ...
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### Relative security of a Vigenère cipher

Within a closed computer network, I am ciphering some plaintext data as an added security measure. This is below several other layers of protection. For various technical reasons, I am restricted to ...
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### Convert numeric message from RSA ciphertext to alphabetic

I have a set of numeric values that are supposed to represent a message encoded via textbook RSA. For example: 60889 37946 13359 61629 35960 13747 I've decrypted ...
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### Complexity of attacks on affine cipher

I am interested in the complexity of attacking affine ciphers under the following two scenarios during a Ciphertext only attack during a Chosen Plaintext attack For an alphabet of size $m$, how ...
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### How to implement the Salsa20 hash function?

I am currently implementing Salsa20 from the specification as an exercise in learning and self-flagellation. I have Sections 1-7 passing the test examples provided. I am now stuck on Section 8, The ...
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### What is the period of a cipher?

For the following explanation of RC4: It is a variable key-size stream cipher with byte-oriented operations. The algorithm is based on the use of a random permutation. Analysis shows that the ...
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### Counter Mode with a sequence of zeros bits plaintext, is it secure?

I had a quiz last week in computer security course. There was a confusing question that I am still looking for a good and clear answer. First, I know that counter mode with a good block cipher is ...
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### What does K stand for in frequency analysis

It was from frequency analysis lecture and the professor mentioned but I cannot recall. The K value for English was .067, German was .076. The lowest K was Russian which was .056. When the frequency ...
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### Cipher for human interpretation [duplicate]

Please suggest algorithms to encrypt and decrypt text messages that can be easily performed by human in a considerably short time. It doesn't have to be really secure, but sufficient to fool ...
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### Is python a secure programming language for cryptography?

I know Python is a powerful programming language but is it secure for cryptography? I mean is it possible to reverse engineer the program (written in python) and discover the algorithm of cryptography ...
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### Automated testing of cipher security for import/export compliance [closed]

What do we know about systems that automatically test and grade cipher security. The application in mind would be for checking for compliance with import/export regulations. I imagine a system that ...
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### Is ASCON cipher broken?

http://eprint.iacr.org/2015/030 present several attacks of ASCON but does not have a conclusion section. I'm having troubles estimating what are the consequences on the use of ASCON. What's your ...
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### What would be the best plain text Cryptography method without the use of a computer? [closed]

What would be the best Cryptography method without the use of a computer? This could be a list of the current options available, that could be used without the use of a computer ...
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### Dancing confusion with Daniel J. Bernstein's stream ciphers

I know of Salsa20 which won the ESTREAM competition. This is dated of 25 Dec 2007. There is also the ChaCha20 stream cipher (cr.yp.to/chacha.html). This claims to increase the amount of diffusion ...
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### SHA1 - SSL/TLS Cipher Suite

SHA-1 is on the way to deprecation, in particular for digital certification (x509). But I can't find ressources about SHA-1 deprecation from SSL/TLS Cipher Suites. Is it implicit, as deprecation ...
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### How to perform frequency analysis of a substitution cipher using a Base64 alphabet

Let's imagine a cipher that works like the following: Plaintext is encoded to Base64. The characters in the encoded plaintext are substituted with a randomly shuffled character set(A-z, 0-9, -, _, ...
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### Do data-dependent rotations have any advantage over fixed rotations?

There are many ARX ciphers, however most use fixed rotations. I know data-dependent compared to fixed rotations are: patented harder to implement constant time more expensive in hardware harder to ...
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### RC4 encryption/ decryption with hashing

I am working on RC4 encryption/ decryption algorithm based on the following: A wants to send M to B, for that A did: H = Hash (K||M) C = Ek (M||H) A sent ...
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### Multi-round Transposition/Playfair as a secure hand cipher in the computer age

Given that computers can be easily compromised, there is a need for a hand cipher that can withstand computer attack. Clearly the traditional hand ciphers fail. One time pads work. They also have ...
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### Type of cipher used where ciphertext has no discernible pattern, spaces. Type?

What type of cipher could give ciphertext where for example random ASCII chars between say F-z (symbols and numerals inclusive), but with only a few spaces? Frequency of chars shows some similarities ...
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### Frequency analysis of Vigenere Cipher

For Vigenere cipher, I understand Find period first (say we have p = 6) Find highest frequency of letter in each group (from 1 to 6) and assume it is "e" in plaintext What if we have more than ...
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### Does the transposition cipher have a network application?

So I'm reading a chapter in my networking book and it talks about substitution and transposition ciphers (Transposition Cipher Wikipedia). I know that most network security uses public key or ...
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### Prove that the affine cipher over Z26 has perfect secrecy if every key is used with equal probability of 1/312

Prove that the affine cipher over Z26 has perfect secrecy if every key is used with equal probability of 1/312. Just some guidance/help with this problem would be greatly appreciated not sure how to ...
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### Need help solving a shift cipher problem?

A three letter alphabet {a, b, c} has probabilities p(a) = .5 and p(b) = p(c) = .25. A shift cipher is applied to pairs of letters. More precisely: plaintexts consist of two-letter sequences of ...
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### Encrypt a Zip File with Caesar Cipher

I'm trying to understand, why the Filesize of a Caesar Cipher encrypted foo.txt.zip File is smaller than a Caesar cipher encrypted foo.txt File. For example: Foo.txt size: 90bytes foo.txt.Caesar.enc ...
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### Block Cipher Modes

I have a question here asking the following: Why do block ciphers need the use of blocking modes? To encrypt messages larger than the size of the block. To avoid having the same block ...
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### Need help solving message encrypted on an Enigma machine?

So basically I'm in a class an one problem we were given a while ago was one involving an enigma machine and a few messages. I do not have any idea of how to approach it, and I really need help. The ...
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### Cipher built from GPU primitives [closed]

Is it feasible to build a cipher (or hash) out of GPU or DSP primitives (e.g. big matrix multiplication, Fast Fourier Transform, big block SIMD, or hardware H.264/AVC codec)? Preferably those are slow ...
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### Chi-Squared Step of Vigenere Cipher Decryption

So, I have been assigned an assignment where I had to solve a Vigenere cipher. Following along with this webpage I managed to get all the way to the chi-squared step. But, that is the problem. Upon ...
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### Isn't a simple Vernam cipher as secure as known symmetric key algorithms?

I have just read little about the Vernam cipher and the problems of implementing it. But, in practice, would not the key, if generated by a commonly used programming language's ...
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### Perfectly secure shift cipher

Prove that if only one character is encrypted using a shift cipher, then the shift cipher is perfectly secure. I want to show that $P(P=p | C=c)=P(P=p)$. But I don't know how to relate. Can anyone ...
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### Do any non-US ciphers exist?

Plenty of ciphers come out of the USA from government research or selection competitions. AES and DES are examples. Are there any public ciphers produced by other states, China or Iran for example? ...