4
votes
0answers
97 views

What informal indicators exist for estimating the computational infeasibility of cryptographic problems?

When assuming a block cipher primitive is secure, or a number theoretic problem is hard, this assumption is usually based on how far we are from breaking the primitive or solving the problem using ...
4
votes
0answers
292 views

Is there a “brainwallet” for GPG keys? [closed]

“Brainwallet” is a program that takes a passphrase (hopefully a good one) and deterministically creates a Bitcoin wallet. This wallet can be used for transactions, then deleted from the computer. To ...
4
votes
1answer
292 views

Complexity class of an idealised version of Bitcoin's proof-of-work (hashcash)? [closed]

To formulate this question precisely, I will define an idealized hypothetical "perfect" hash function $H(n)$ which has nice scalability properties, and will formulate a problem PERFECT HASHCASH in ...
4
votes
0answers
745 views

Reasons for Chinese SM2 Digital Signature Algorithm

In the IETF RFC draft named "SM2 Digital Signature Algorithm" a signature algorithm is specified. The RFC does however not mention why this signature algorithm has been defined. Nor does it specify ...
4
votes
0answers
151 views

Unique GCM/CCM initial counters without recipient side message counters

I am implementing the encryption layer for a communication protocol. The bulk encryption method used is either AES-CCM or AES-GCM. Due to implementation details, encryption of packets is usually, but ...
4
votes
2answers
2k views

Are there any standards of multi-prime RSA key generation?

FIPS 186-3 specifies a method to generate DSA parameters. Is there anything similar (official standard or widely-accepted recommendation) that shows how to generate the primes for multi-prime RSA?
4
votes
0answers
186 views

Ring Signature - paper/code difference in trying to solve inverse trap door function?

there is a paper on ring signatures and a python implementation of it here. The Step 4 in the paper describes $y_s = v =C_k,_v(y_1, y_2, ... y_r)$ for all $1 \leq i \leq r$ where $i \neq s$. The ...
4
votes
2answers
289 views

AES-CTR with ephemeral keys vs IV

Let's say that we have a key exchange of some sort, which leaves A and B sharing the long-term secret $S$. Then, A and B want to use AES-CTR for the communication, which leaves us with several ...
3
votes
2answers
925 views

Generate RSA-2048 private key for a VERY fast decryption (don't care if it will be unsecure)

Given public standard RSA exponent e = 65537, is there any (d, n) pairs so that RSA decryption becomes a trivial operation? The modulus n must be no less than 2048-bit. The goal is to get a real ...
3
votes
4answers
618 views

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? ...
3
votes
3answers
552 views

Is there any area where AES-CBC cannot be used ? If so, why ?

I would like to know the domains or specific applications where using AES-CBC is not advised due to any drawbacks like sequential encryption of AES-CBC ?
3
votes
5answers
2k views

Using one-way hash functions as the encryption method

Suppose two parties want to communicate securely with each other (Bob and Alice) using a simple messaging system in English. There are approximately 180,000 currently used words in the English ...
3
votes
1answer
521 views

Why does “2xAES-256” provide “99.99%” security strength whereas “1xAES-128” provides “40%”? [closed]

I recently was "directed" to FlipsCloud, a company selling security solutions (as far as I can tell). In particular I've investigated their page and found a page on their "encryption features". This ...
3
votes
5answers
1k views

Approach towards anonymous e-voting

I want to implement an internet-based e-voting system. Voters shall be able to cast their vote for one out of n possible candidates. Each candidate has his own ballot-box kept by and at a trustworthy ...
3
votes
8answers
691 views

Does a public key absolutely need to be used to initiate an encrypted session?

I am a software developer working on an application with the .NET platform. This application needs to provide a secure connection and encrypt all data between the client and the server. It is a ...
3
votes
3answers
720 views

Complexity of arithmetic in a finite field?

I am wondering what the complexities are of adding/subtracting and muliplying/dividing numbers in a finite field $\mathbb{F}_q$. I need it to understand an article I am reading. Thank you
3
votes
2answers
398 views

AES-ECB as an authentication mechanism

ECB is considered to be insecure when used for confidentiality because identical plaintext result with identical ciphertext. But what if we use ECB for authentication? Assume A wants to transmit an ...
3
votes
4answers
1k views

Increased CRC collision probability when adding bits to input message

The Scenario I have a message string I need to transport over a wireless network that may be unreliable. This message string is about 100 bits long, and is packaged with an 8-bit CRC. When the ...
3
votes
2answers
565 views

security of Felix cipher

I just find this pencil and paper cipher 'Felix' and I want to know how secure it is? EDIT From http://web.archive.org/web/20110825142054/http://topcat.hypermart.net/papers/felix.txt Felix a ...
3
votes
2answers
304 views

If Bob steals Alice's private key, how exactly would he read her encrypted documents?

So Bob grabs Alice's secret key when she isn't looking and her encrypted files, doesn't he need to know her passphrase to read her files? What I am reading is that no he does not need it but as far ...
3
votes
4answers
485 views

Verify product without revealing multipliers

Situation: Several participants contribute encrypted random numbers. These numbers will be used to generate community-agreed random (by simple multiplication). Question: Is there any way to detect ...
3
votes
1answer
338 views

Authentication using AES

I need to implement an authentication mechanism in an embedded environment which does not support floating point operations but has an AES accelerator module which allows for encyption/decryption ...
3
votes
2answers
869 views

breaking fully homomorphic encryption schemes

Fully homomorphic encryption schemes allow one to evaluate any arbitrary computation over encrypted data. Intuitively this seems to be too weak, irrespective of how we achieve this. An adversary who ...
3
votes
3answers
393 views

Advantages of 64-bit CPU smartphone

Advantages of having a 64-bit CPU vs 32-Bit CPU smartphone … 3. Complex Encryption. Improved Security: 64-Bit can process incredibly large numbers allowing you to better encrypt data against ...
3
votes
2answers
4k views

What characters does AES output?

From what I understand after testing the Crypto-JS file here: http://crypto-js.googlecode.com/svn/tags/3.1.2/build/rollups/aes.js AES creates encrypted strings that contained letters, both ...
3
votes
3answers
338 views

Is it possible to work out the hash algorithm from a list of known message-hash pairs?

For example, in my situation I know hash(20) = 486e9638177faf1f34e49910491b77af. I also know the hashes for all values from 0 to 20. Is it possible to work out the ...
3
votes
4answers
1k views

Which is more secure using a CSPRNG for a One-time pad, or AES?

In reading about the One-time pad it appears to need truly random key for the pad. Since true random values are not practical to generate this presents a problem (thus making One-time pad less ...
3
votes
2answers
2k views

Different implementations of SHA1, which one is correct?

I have noticed that different implementations of SHA1 give different results. As I'm currently programming my own SHA1 implementation (in MATLAB / GNU Octave), I wonder which one should I follow? ...
3
votes
3answers
375 views

Is the new preprint “An Algorithm For Factoring Integers” by Yingpu Deng and Yanbin Pan worth reading?

I just discovered on the eprint server of the IACR the paper mentioned in the title. Scanning quickly over the paper I didn't find anything spectacular, so I doubt that their new(?) approach will be ...
3
votes
3answers
10k views

Where i can find an AES implementation in python?

Where i can find a "reviewed" version of AES implementation in python. Not an API like PyCrypto whereby you can call AES algorithms in a single line.
3
votes
3answers
726 views

How can I avoid calculating with huge numbers when implementing the RSA algorithm

There is 26-letter English alphabet. There is the plain text: TRYAGAINLATER. I need to encrypt it by RSA algorithm with the public key 53. What is the ciphertext? ...
3
votes
2answers
350 views

Is double hashing collision resistant?

Double hashing can surely provide more security than only one layer of hashing but does that necessarily mean it is more collision resistant? This question in a more mathematical form: If $H$ is a ...
3
votes
1answer
2k views

Why is Serpent faster than AES in this benchmark?

I have a laptop without the AES-NI CPU instructions but with SSE4.1. I'm using Linux and tried the (in-memory) cryptsetup benchmark to get the rough tendency which returned: ...
3
votes
2answers
331 views

Is prime regeneration necessary for every new session using a Diffie-Hellman key exchange?

As I understand it, bruteforcing a Diffie-Hellman generated secret key takes $P-1$ attempts to crack the shared secret, where $P$ is a very large prime used for modulus. If your $P$ is quite large, ...
3
votes
2answers
769 views

Combining LFSRs for Stream Ciphers: Why do we need high non-linearity?

Linear Feedback Shift Registers (LFSRs) can be excellent (efficient, fast, and with good statistial properties) pseudo-random generators. Many stream ciphers are based on LFSRs and one of the possible ...
3
votes
3answers
564 views

How to avoid a chicken and egg scenario with encrypting passwords?

I am working on application that allows users to upload files containing company data and then share those files with a list of other users that have specific roles within the system. I want to ...
3
votes
3answers
551 views

Can I pre-define the points in Shamir's Secret Sharing algorithm

With Shamir's secret sharing is it possible to pre-define the points returned by the algorithm? For simplicity if I have (k, n) where k=2, and n=4, and I have the points X,Y,Z, and Q. Can I create ...
3
votes
1answer
9k views

How to solve MixColumns

I can't really understand MixColumns in Advanced Encryption Standard, can anyone help me how to do this? I found some topic in the internet about MixColumns, but I still have a lot of question to ...
3
votes
3answers
2k views

How do public key rings work in cryptographic applications?

I am wondering if there are any links to articles or resources available online, or explanations that you can give, that would help me to understand the concept of a public key ring, and why I might ...
3
votes
2answers
1k views

How can I break REDSHIRT / REDSHIRT2 encryption?

Recently, a user on Gaming.SE asked a question about whether the user password in the video game Uplink could be modified after being initially set. The game does not contain an option to change the ...
3
votes
2answers
362 views

Why not use an algorithm's code rather than data itself for one time pads?

Instead of using actual data for one time pads, what would be different if the code for an algorithm was exchanged so that to acquire the pad one would execute the algorithm and use its output? Why ...
3
votes
2answers
316 views

Can you help with that definition for a CCA?

The following is a definition taken from Introduction to Modern Cryptography by Katz and Lindell. I'm having a hard time understanding some basic concepts! Can you please help me? ...
3
votes
4answers
352 views

Combining several symmetric ciphers using XOR

I have seen a talk by Rüdiger Weis, where he says that you can combine two symmetric ciphers using XOR. According to him, that has the effect that its sufficient if only one of the ciphers is secure. ...
3
votes
2answers
205 views

Key space vs Cardinality of 1024-bit RSA

I have been trying to figure out the encryption key space, and cardinality of 1024-bit RSA. From my understanding, the key generated from 1024-bit will be primes greater than $2^{1023}$ but less than ...
3
votes
2answers
312 views

Small Prime Difference in RSA

In RSA, the $p$ and $q$ should be randomly generated, and they are the same size. The difference between $p$ and $q$ should not be small. Suppose that $u=|p-q|<20$ and $p \times q ...
3
votes
3answers
422 views

Regarding Key Strength with DES and Blowfish

I had a small discussion with my friend on combining two encryption algorithms based on 64-bit keys. Say I have a plain text of 64 bits which I want to encrypt. My Key size is 128 bits. I will use ...
3
votes
2answers
1k views

How long does it take to crack PBKDF2?

How much time will it take to crack PBKDF2 while using a 9 character password? I'm not specifying any specific system or platform. If a brute force attack is made using the best ever super computer ...
3
votes
4answers
700 views

Which tamper-protection algorithm provides the shortest output?

Background When making web applications you sometimes need to pass data along with the form which isn't visible to the user. Database IDs are the most common, but texts and IDs are sometimes ...
3
votes
2answers
273 views

Should I bother implementing DH + AES, or leave it to a library like Crypto++

I'm making a C++ back end for an application that'll heavily rely on AES-256 and DH. Should I trust third party libraries, or spend (lots of) time to learn about cryptographic implementation and write ...
3
votes
2answers
802 views

Theoretical pi-based stream cipher

Let's pretend that all digits of pi are known and arbitrarily long sequences of digits are trivial to get. Further, some mathematician proves that there are no patterns in pi. We could create a stream ...

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