# All Questions

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### Need help with PKCS#12 3 key triple des key expansion

I am trying to decrypt PKCS8-Shrouded Key Bag inside a PKCS#12 pfx file. The oid for the encrypted data is PbeWithSHAAnd3-KeyTripleDES CBC. Iteration count and salt has been provided within the pfx ...
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### How does RIPEMD160 pad the message?

For RIPEMD hashing algorithm on hardware I am not exactly getting how padding works So as per my understanding padding will work like explained below: For ripemd 160 message should be multiple of ...
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### What is the complexity to break second preimage resistance?

In the context an of hash functions we have three required properties. Preimage resistance Second preimage resistance Collision resistance. The bounds for Pre image collision is $O(2^{n-1})$, the ...
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### implementation of authenticated encryption algorithms on GPU

I am trying to implement an authenticated encryption algorithm on GPU. i have selected an algorithm that can be parallel both in Enc and Dec. this new authenticated encryption algorithm has a small ...
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### Classification of a stream cipher

How would one classify a stream cipher that is neither synchronous, nor self synchronizing? I would have thought asynchronous, but from all the sources I can find, asynchronous is synonymous with ...
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### Computing inverses in a binary field

Please suggest how can i solve the below question What is the inverse of {03} in GF (2^8) with the irreducible polynomial x8+x4+x3+x+1?
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### Effects of varying the key size for AES encryption [closed]

How to investigate effects of varying the key size for aes algorithm encryption of data over the communication channel
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### Elliptic curve ElGamal with homomorphic mapping

I am interested in ElGamal due to the fact that you can achieve some degree of homomorphic properties. I became interested in applying ElGamal to elliptic curves, and found this other question with an ...
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### Would a Rubik's cube be a trapdoor function?

It's easy to scramble a Rubik's cube but it is hard to solve, unless you know the algorithms for solving it. This makes it a trapdoor function, correct?
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### SHA1 collisions and the impact for ECDSA signatures

What will it mean for ECDSA using SHA1 when we have practical attacks breaking the collision resistance property of SHA1? [UPDATE] Added a bit more details to be clear. If $(r,s)$ is the ECDSA ...
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### Help with AES decryption with AES-NI Instructions

I am in process of implementing a AES 128 encryption in AVX2 assembly (using AES NI), and am having some problems with decryption logic. I have implemented the encryption sequence without any trouble. ...
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### Can an AES-256 key be generated for a large number of cribs? [duplicate]

I have a question in regards to Ransomware type viruses. I know that a number of these viruses use the AES-256 algorithm to encrypt user's files using a randomly generated key. I work in IT support ...
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### Multiparty encryption and decryption

Is it possible to send a single encrypted data message to multiple users so that the users receiving the message can only decrypt certain parts of the message, depending on their rights. For example, ...
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### Difference of full codebook and non full codebook

While reading a paper about Dynamic cube attack, I saw two terms: full-codebook and non-full-codebook attacks. What do they mean? What is the difference? Regards
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### hashing algorithm [closed]

I have a program which takes an input of username, the a password and then hashes it and gives integral output. It is not fixed for a particular character. I want to know its hashing algorithm. I ...
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### Is there any code implementation of the HMAC-DRBG PRNG? [closed]

I'm looking for the code of HMAC-DRBG in either C# or C++, for use in a cryptography related project. I can't find it anywhere. Would appreciate the help! Thanks a ton!
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### Can one passively load-balance HTTPS traffic based on TLS SNI?

Is it theoretically possible to passively snoop into the HTTPS traffic, reliably detect whether or not TLS SNI is attempted to be used by the client, and, if it is, redirect the stream of the ...
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### A way of bruteforcing a hash value without the use of file [closed]

An example is better than explanation. Let's say we have this md5 hash : 15e0adc0213e01ec44acee74ed4ece5b All I know is this hashing method is md5, the length of ...
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### Shamir SS: To associate shares to the public values $x_i$, when the shares are permuted [duplicate]

Suppose we use $(t,n)$ Shamir secret sharing as follows: We share the secret $\beta$ as $S=[s_1,..., s_n]$, where $X=[x_1,...,x_n]$ are the public values. For the sake of simplicity, lets assume ...
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### MAC algorithm difficulties

Can anyone explain to me why this is a bad idea? I cannot see anything wrong with it except that key K should be different for MAC and AES. MAC algorithm consists of letting the MAC of message M ...
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### total effective key length of the AESX-192

If I have a AESX-192 be a block cipher which is similar to DESX but has the DES being replaced by AES and the AES key size is 192 bits. How should I compute the total effective key length of the ...
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### steganography of an mp4 file [closed]

I have 2 mp4 files that might have something hidden in them. I have been using OpenPuff because it is the only app I can find that will handle mp4's. When I go to unhide and try to load the video(s) ...
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### how to define the Truncated Polynomial?

In NTRUEncryption, I seen the trucated polynimials, but I cannot understand the trunacated polynomial calculation. So, could tell me anyone How do we calculate the truncated polynomial?
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### Why does image size increase after steganography?

I am working on a steganography technique. Sometimes I need to send my steganographed images online to my friends but in the process the image gets compressed destroying all the data. I found ways to ...
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### Proving property of Modified Rabin Signature

I'm trying to prove one of the properties of the “Modified Rabin Signature Scheme”: If $gcd(x, n) = 1$, then $x^{\frac{(p−1)(q−1)}{2}} \equiv 1 \pmod n$ This is what I’ve got so far… Proof Let ...
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### Identify encryption method [closed]

I have a large string containing upper and lower case characters as well as digits. It contains "==" at the end of string. How can I decipher this string?
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### Any stream cipher with avalanche effect?

As far as I know, all stream ciphers work by generating a stream of pseudo random bytes, and XOR it with the plain text to get the cipher text. It has the property that one bit change in the cipher ...
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### Need help in solving this cryptographic puzzle [closed]

John and Alice came home to find their window broken. Inside, they found a brick with the following note tied to it: ...
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### Re-encrypting this decrypted data

I got this data: ...
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### Is there a standard for hashing a list of strings?

I'm working in Python, and my goal is to hash a list of strings with a cryptographic hash function such as sha256. It would need the property that a change in any string, or the order of the strings, ...
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### how to determine block size for decryption

a message coded with RSA is broken up into blocks, then padded/transformed prior to encryption via modular exponentiation with the public key. However, the encryption result for each block is not ...
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I need to store passwords for a web application, and was looking at Bcrypt for a possible solution. After some research, it appears only the first 72 bytes influence the final hash output. While it is ...
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### RSA algorithm private key extraction

Decrypting messages can be done by using the following formula: $$M = C^d \mod n$$ Where $M$ is the decrypted message, $C$ is the encrypted message and $d$ is the private key Theoretically ...
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### Exactly how bad is using 'mod' to clamp reduce numbers to a given range?

Let's say I'm naive and want to generate a random integer in the range [0, m), so I do the following: ...
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### RSA numerical questions

Let $n$ be the modular arithmetic, $p$ and $q$ the two large primes such that $n=p*q$ and $e$ the public exponent. Here they are two "simple" numerical questions: If $p = 13$ and $q = 17$, what is ...
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### How exactly does certificate based authentication work?

I know the concept of key generation, as well as encryption and decryption using public and private keys. When it comes to authenticating a user by a server, in general there are three types: ...
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### Bilinear pairing using jPBC in Java [closed]

How to generate Bilinear pairing in Java using jPBC? How to find the generator g which satisfies Non-degeneracy condition e(g,g)!=1
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### Is this DIY remote lock protocol secure?

I need your advice on following scheme of exchange protocol between remote lock and key. I'm planning to use following algorithm: Key generates unique value that never repeats (in reality it's just ...
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### Security for secret key of server in Identity-based Encryption

In the key set up phase, server generates Pub=s.P, where s is the secret key.Then , it gives clients Pub,P as public parameters and pairing descriptions. Is it possible for clients to pre-compute r.P ...

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