# All Questions

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### How does a Hashing algorithm always result in a digest in a fixed size?

This question revolves around the Hashing Algorithm attribute that the resulting digest is always the same size (also known as Fixed Width). For example, whether you hash the word "hello", or 10gb ...
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### Factorizing N to derive D

So I have the value of N. I have to use this value of N to find the value of D. N = 265291078722948385089717069136983657793 Now I read about RSA algos and found out that ...
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### Do low-entropy fingerprints actually make any sense?

I'm thinking of ZRTP and OTR in particular here. From my understanding, after a Diffie-Hellman session is initiated, the shared secret is then hashed into a 4-digit number, which the two parties can ...
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### What is the use case for XOF functions (i.e. SHAKE128/256)?

FIPS 202 defines 2 functions: SHAKE128 SHAKE256 As extendable-output functions (XOFs) that can have variable output length. But in Appendix A.2 marks: it is possible to use an XOF as a hash ...
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### Time complexity of trial division

Suppose $n=pq$, where p,q are prime numbers. let $p ( \le q)$ be the smallest prime, then we know that $p \le \sqrt{n}$. In trail division, we check $n \mod i$ for the values of $i$ from 2 to ...
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### Help with pseudorandom functions

I started a new lecture this year about crypto and I've had a few problems in the first few weeks with the exercises we got. I would appreciate a "guide" on how to solve problems like the following ...
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### Are all encryption tools made equal?

I'd like to encrypt work-related data backups stored on an external drive. The backups contain proprietary company information and trade secrets. My current backup program, Comodo Backup, allows me ...
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### Is there any relation between two strings with the same MD5 hash?

Is there any relation between two strings with the same MD5 hash? For example these two strings: ...
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### what problem happen if we always use IV Zero in CBC Mode? [duplicate]

i have a question about CBC operating mode. what problem happen if we always use IV Zero in CBC Mode?
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### Why we use operating modes in cryptography? [duplicate]

Why we use operating modes (CBC , . . ) in cryptography? i mean what is the essential of use it ?
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### Relationship between exponent and modulus in RSA (as RSA properties as listed in X.509)

In one of my assignments, I had the following question (Please read on. Not a homework assignment :) ): X.509 (1998 version) lists properties that RSA keys must satisfy to be secure. One such ...
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### Is it true that 7zip doesn't use any salt with its KDF?

This issue claims that 7zip does not use any salt with its key derivation function: https://github.com/magnumripper/JohnTheRipper/issues/1679 If that's true, wouldn't that mean you can crack multiple ...
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### Modular arithmetics in diffie-hellman

Studying the basics of Diffie-Hellman key exchange, I'm stuck at a basic operation used in the end of the key exchange (where you show that both computations actually are the same). Can someone ...
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### IV re-use for Salsa20 [duplicate]

Are their any specific requirements for the IV when using Salsa20? Is it for example allowed to re-use the same IV when encrypting with the same session key? Should the IV be random? etc I tried to ...

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