# All Questions

116 views

### Known plaintext, unknown 128 bit block cipher

I have an encrypted configuration file from an embedded device which I'm trying to decrypt. The file seems to be encrypted in 128bit blocks, as changing a single option causes a 16 byte block to ...
23 views

### Transport SA bundled inside a tunnel with encryption applied before authentication?

For IPsec I am considering different formats of ESP encryption and authentication. I am not sure what happens with "Transport SA bundled inside a tunnel with encryption applied before ...
235 views

### Why is AES unbreakable?

Why is it said that AES is unbreakable? Brute force attacks would take years to crack it, so is it possible to crack it if the computational speed of machines increase in the following decade?
30 views

### how to integrate 2-3 algorithms to encrypt large data fastly and securely insted using AES? [closed]

I am thinking to build an encryption algorithm which take less time when encrypt large data such as video,mp3 and which has security credential.
42 views

### What work goes into creating new asymmetric cryptosystems?

It's seems to me that it is rather easy to create a symmetric encryption algorithm (though not necessarily a secure one). They're a dime a dozen. The number of asymmetric encryption algorithms ...
39 views

### Separate keys for encryption and MAC? [duplicate]

I use HMAC(ciphertext)+ciphertext for authenticated encryption. The same key is used for both MAC and encryption. Is that right? Is using separate keys for MAC and encryption necessary or any good? ...
85 views

### How do SignRecover and VerifyRecover work?

In PKCS#11, there are the SignRecover and VerifyRecover methods, where the data can be recovered from the signature. How do these methods work? Can I implement signrecover and verifyrecover with ...
46 views

### Can IGE mode be parallelized?

As far as I know, in IGE mode (infinite garble extension) each block depends on the previous one. In that case, can the encryption be parallelized? Is there some way to do it?
19 views

### Looking for an adjustable compute bound decryption function

I'm looking for a way to decrypt data, but make it require varying amounts of CPU power to do so. Maybe this could be illustrated as e(m) = m' and ...
85 views

### Problem with testing MD5 collisions

I am trying to test MD5 collisions presented in “Collisions for Hash Functions MD4, MD5, HAVA” (PDF) by Xiaoyun Wang, Dengguo Feng, Xuejia Lai, Hongbo Yu; 2004. I wrote a PHP script to test it, but ...
33 views

### What is the best authentication logic to analyze RFID (randomized hash-lock) authentication protocol?

What is the best authentication logic to analyze RFID (Randomized hash-lock) authentication protocol, (Ban logic, GNY logic, SVO logic, VO logic, AT logic) or another one?
120 views

### Is there a format preserving cryptographically secure hash?

I want a way to 'scramble' strings (like words, names) in a predictable way but I don't ever want to (myself or anyone else) be able to 'unscramble' the strings. I found that perhaps what I am ...
85 views

### Will SHA1 or Other Hash Functions Ever Contain Quotes [closed]

I feel foolish asking this, but will the hash generated by SHA-1 or other encryption methods ever have the possibility of containing a quote? Or any other characters that may be escaped such as ", ', ...
35 views

### Is the half-homomorphic property of RSA a problem for blind RSA signatures?

For blind RSA signatures, is it problematic that RSA is half-homomorph? Take a scenario where blind RSA signatures are used for something like a voting procedure or this proposal: Lots of people, ...
75 views

### Defence against timing attacks

I know this is a difficult subject but would a good defense against timing attacks be not sending a message if the decryption or authentication fails? So if the attacker provides a wrong HMAC for ...
38 views

### AES mode scheme feedback [duplicate]

I've been studying encryption on a hobby basis, and wanted to know if I got this basic cypher construction right (this is another experiment, see the AES ECB experiment thread earlier). Encryption: ...
115 views

### How difficult is it to get a key using simple XOR

Recently someone gave me an algorithm as follows: XOR = Key XOR Random1 XOR Random2. They think that in order for someone to extract "Key" from XOR they would need Random1 and Random2.. but looking ...
63 views

### AES key from encrypted text and VI

So I'm trying to figure out if it's possible to extract the private key if you have the ciphertext and the IV corresponding to that ciphertext. It's for some kind of a challenge, and can't really ...
68 views

### Find the prime factorization in the DLP

Suppose we have $g^x \equiv h \pmod N$ Where $N = pq$ and $p$, $q$ are distinct primes. Also $(p-1)/2$ and $(q-1)/2$ are primes. If we know what $x$, $g$ and $h$ are, is it possible for us to know ...
33 views

### AES different modulo operations

I don't get the modulo 10001 operation in mixColumns so much. If I have to take the byte computations mod 100011011 anyway what leads me to a result of 4byte length, why do I need the mod 10001 ...
11 views

### Difference between Kerberos and GDOI? [migrated]

What is the difference between Kerberos and GDOI, I know first is more toward authentication and latter is more toward multicast key management, can I use Kerberose protocol in GDOI for server and ...
65 views

### Is the reduction from left-or-right IND-CPA to real-or-random IND-CPA tight?

A modern trend in cryptography consists of defining security as rigorously as possible, and then designing schemes which are secure according to those definitions. Proving security comes in the form ...
101 views

### Is CBC theoretically harder to brute force when compared with ECB?

Theoretically is CBC mode harder to bruteforce when compared with ECB? Assumptions We ignore computational cost for the XOR operations IV is made public
120 views

### AES as Integer Program

I read that AES can be broken by solving a Linear Integer Program (IP). From a given encrypted text, how can one construct this IP? How big is the system?
54 views

### Koblitz encoding a message to a point, what is the “associated auxiliary base parameter”?

I am looking at the Koblitz method for encoding a message as an elliptic curve point. The first step given in the paper I'm reading is: "Choose an elliptic curve and its associated auxiliary base ...
73 views

### DH and PKI for KeyExchange

My question is fairly simple. I have more than two nodes which needs to communicate very efficiently from computational point of view. One of the nodes can become a coordinator between the nodes. ...
68 views

### Performing differential cryptanalysis for randomly generated S-boxes

As far as I know, performing differential or linear cryptanalysis always requires a knowledge of the S-boxes' content and order. Yet in Bruce Schneier's Applied Cryptography, it is stated that random ...
127 views

### How to compare between two cryptographic algorithms in terms of security? [closed]

How to compare between two cryptographic algorithms (e.g. SHA-1 and SipHash) in terms of security? That is, how could one prove that algorithm X is more secure than algorithm Y?
42 views

### Will the complement of a 64-bit key and message produce the complement ciphertext if ECB is used in DES?

Say I have a 64-bit message/key: P1: 1011....... K1: 0101....... I run this message/key pair through DES in ECB mode and obtain some cipher that looks like the ...
109 views

### What is the advantage of using the socialist millionaire protocol to authenticate vs HMACing some random number?

Say Alice and Bob have a shared secret $s$. Alice and Bob establish an encrypted channel and verify that it hasn't been MitM'ed by exchanging $r_1$ and $r_2$, where $r_1$ and $r_2$ are randomly ...
39 views

### Recombination thresholds in degree reduction of multiplied Shamir shares

Shamir's secret sharing can be considered multiplicatively homomorphic, if one is aware of the fact that multiplying two shares of a (n,t)-threshold shared secret yields a share of the same secret, ...
83 views

### Signing Files vs. Signing File Hashes

What are the security pitfalls that may occur by signing a list of file hashes, versus signing individual files? In short, the security trade-offs between: ...
33 views

### One-one correspondance complete function

I am reading the paper by John B. Kam and Georges I. Davida (1979) titled Structured Design of Substitution-Permutation Encryption Networks. On page 749 it reads ...
34 views

### How to choose the integer m in the general number field sieve (GNFS)?

Given an integer you want to factor $N$, GNFS starts by selecting a monic irreducible polynomial $f \in \mathbb{Z}[X]$ and an integer $m$ such that $f(m) \equiv 0 \text{ mod } N$. In practice, if $m$ ...
53 views

### Is format preserving encryption suitable for use with words or names?

Is it possible to use FPE to encrypt names and language words like 'Bob' 'the' 'tree', in order to preserve both length and format (like keeping characters within a certain range like A-Z a-z) The ...
32 views

### Pseudorandom function and hash function [duplicate]

What is the difference between a pseudorandom function and hash function ? I have already read the answer in this link What is the difference between a hash function and a pseudorandom function? but ...
44 views

### What are the steps to decrypt a TLS 1.1 record?

My question is related to another question in Cryptography about TLS 1.1 and 1.2. I have read both RFC 2246 The TLS Protocol Version 1.0 and RFC 4346 The TLS Protocol Version 1.1. What I know is that ...
610 views

### 128 bit 3DES Key and AES Key: what's the difference?

Apologies if this is really basic but I couldn't find the answer to this. I have heard some Info Sec colleagues talking about creating an AES key in preference to a DES or 3DES key but I don't know ...
59 views

### Are there cryptographic schemes that mask as unencrypted traffic?

Are there cryptographic schemes that make encrypted traffic look like unencrypted traffic?
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58 views

### Why would cryptography fall apart if there were a finite number of primes? [closed]

I vaguely know that prime numbers are very important in cryptography, but I assume for most encryption methods, they tend to stay rather 'small'. Are we really using massive prime numbers for ...
62 views

### How does ccrypt work?

On many Linux/GNU distributions CCrypt (ccrypt) by Peter Selinger is available as a command line utility to encrypt files. How does the protocol work and is it ...
55 views

### Calculation of time needed to crack DES with my CPU

I have a laptop that has the CPU and the RAMs shown below in the images. My question is that, using this CPU and the RAMs, how much time would it take for me to crack an old school DES algorithm ...
26 views

### BLAKE2 input parameters [migrated]

Being a newbie, I was reading papers on the recent crop of hash functions and BLAKE2 intrigued me. Then I wanted to play around with the "blake2s" code in the code package. If I were to implement a ...
102 views

### Twofish vs. Serpent vs. AES (or a combo)

I've seen some posts and info online, but they are from 2009, 2010, 2011 or 2012, which is 3-6 years ago, which is a very long time. So I'm looking for an up-to-date answer about which of these is the ...
61 views

### How obvious is it to decrypt numerics encrypted with a reused one time pad?

For instance say you encrypt text using the one time pad and you end up with some scrambled text that appears illegible. If you reused the key for multiple times for enough text, someone could ...
93 views

### How does $g$ being a generator imply Diffie-Hellman's correctness?

In the Diffie-Hellman protocol for key exchange over an unsecured channel, we choose $p$ and $g$, where $g$ is a generator of $\mathbf{Z}_p^*$. However I want to know why this assumption makes the ...
39 views

### Differences between Work Factor and Time Complexity

I am interested to know if work factor means the same thing as time complexity. Quoting Work Factor : Uncovering keys in cryptosystems The Work Factor of a cryptosystem is related to its ...