# All Questions

100 views

### Distribution based integer factorization

The past week I've been looking into - and playing with - algorithms for factoring RSA moduli. From what I understand, it's important that the primes p and q are of the same magnitude as the square ...
195 views

### How to check that you got the right key when brute forcing an encryption?

How do you know when you have the right key when brute-forcing? Let's say that they test the right key. They then have to check that the decrypted text makes sense. To do so, they can test whether ...
3k views

### What is a “freestart collision”?

In their work on SHA-1 collisions (cf. the currently unpublished paper “Freestart collision on full SHA-1” by Stevens, Karpman, and Peyrin) Stevens et al show that they are able to generate "freestart ...
69 views

### Does a stream cipher provide perfect secrecy?

From WAR10CK here: If I actually do create a machine using RC4 or AES-CTR and have a TRNG continually feed it a constant steady stream of random bits. Provided that the stream of bits is purged ...
139 views

### help with cryptanalysis of a sponge permutation

I have been studying and researching hash functions. So far my research has led me to the sponge construction. It appears that the permutation used in the sponge to stir the state is more or less ...
81 views

### What does the comma mean in m, c := E(K, m)

Disclaimer: I'm a beginner to cryptography. Background: I'm reading Cryptography Engineering by Ferguson, Schneier, and Kohno, where the authors use this image: Question: What do the commas mean ...
72 views

### How to overcome issues with big ciphers? E.g. with small vs. big Vigenére Ciphers

I understand that bigger ciphers show more recurring patterns and therefore should be easier (or at least faster) to decrypt as you'll have a better statistical analysis, being However if we use a ...
310 views

### Small subgroup confinement attack on Diffie-Hellman

I am trying to understand the small subgroup confinement attack on the Diffie-Hellman algorithm. I will present the attack and try to explain why it works. Small subgroup confinement attack on the ...
71 views

### For enciphering messages with AES in CTR mode, do I need a different key for each message?

I have written a program to run AES in CTR mode with keys of 128,192 or 256 bits and checked it gives correct results with the data given in section F.5 at ...
69 views

### Implicit authentication aritcle

First, I want to know what is the logarithm used in the following system of equations (from the paper Flexible and Robust Privacy-Preserving Implicit Authentication - Domingo-Ferrer, Wu, ...
78 views

### Would adding daily changing nulls in front of their messages have made the Engima harder to crack?

The British decrypted the German enigma because they knew that they would repeat the message key twice at the start of every message. Of course, technology to encrypt enigma without the repetition ...
71 views

### the decryptNode function for leaf nodes in CP-ABE

can someone please explain to me why decryptNode gives as result e(g,g)^rq(0) for leaf nodes, i don't understand how they went from the sconde step to the third ...
95 views

### Exponent operation over element of G

I found a definition of an exponent operation over the element of $\mathbb{G}$ in this paper (page 4): $$(g^a)^{\% b} = g ^{a \text{ mod } b}$$ I couldn't understand the rest of the paper (Decrypt ...
40 views

May I know what method should I use to solve question #3? I totally don’t understand it and I can not find any things about the clocking pattern on the internet. Is it still using LSFR to ...
20 views

### TPM specification physical presence requirements

I am looking at TPM Main-Part 1 Design Principles_v1.2_rev116_01032011 and on page 69 of pdf, equivalent to page 57 of the document itself,there is comment on physical presence as follows: "Observe, ...
97 views

### How secure is this modified Bazeries Cylinder?

This device is a modification of the Bazeries cylinder, it has two stacks of 5 rotors which each bear two alphabets plus numbers 0-9, one in correct order and one in random order ( 36 characters in ...
29 views

### SSL Traffic Inspection

Is the firewall decrypted my session? There is an error "Certificate Not Trusted" (Server Certificate changed to Firewall Cyberoam Certificate). Which public Key I got? Is Main server Public Key or ...
163 views

### How to generate a bilinear group of prime order p for key generation

I am trying to implement an IEEE Paper In Cryptography. I read many reference regarding an RSA key generation. But i am confused with above statement. Please someone explain me What it says with ...
59 views

### RSA-OAEP: How does it work?

I was looking at this image about OAEP: ..and was wondering what was happening here. We have a data block DB which consists of: ...
34 views

### Hiding the identity of a party within the Kerberos authentication scheme

In the Kerberos authentication protocol, as described here: would it be safer to replace step (1) with: $$A \rightarrow T : A, E_{K_A{_{T}}}(B, N_A)$$ so that a passive adversary does not know ...
122 views

### How to enforce data privacy, integrity and authenticity of distributed firmware images for an embedded device?

I'm developing a bootloader for an embedded device, with which it should be possible for customers (i.e. device owners) to update the device's firmware. It is required that: the firmware is ...
175 views

### Transforming Gaussian random $[0,1]$ numbers to uniform $[0,255]$

I am not exactly sure if this is for math stackexchange or crypto: A TRNG outputs numbers in $[0,1]$ in a Gaussian distribution. I would like to convert them into uniform random bytes ($[0,255]$) to ...
12 views

### Breaking El Gamal defined over Sn

How can we break EL-GAMAL Encryption defined over Sn the permutation group ? Kindly give the efficient algorithm for it.
43 views

### Length of encryption password aes-256-cbc

I'm encrypting a file with sensitive information with cat secret | openssl aes-256-cbc -a -salt > secret.enc I am choosing a random encryption password with ...
54 views

### Smart Card choice for PKI implementation

I'm seeking to implement a national digital signature standard on a smart card. I feel like this is a good place to ask if anybody is acquainted with a hardware supplier offering smart cards that ...
55 views

### Do you need a HMAC if decryption attempts are severely limited?

I am considering an application where data bandwidth is extremely limited, and considering removing message authentication codes from encrypted transmissions. The encryption method is currently ...
12 views

### Two nodes in p2p network exchange data and read data in same time [on hold]

I want to finde paper about exchange data between two nodes in p2p network. They must read each other's data in same time. In example two player a,b play rock scissors paper. A must read b's data ...
43 views

### Tackling encryption problems with “Zipf's law”?

I am new to cryptography and was wondering if it would be possible to semi-reliably "decrypt" an encrypted message by using the statistical distribution of symbols (/letters/numbers) in the encrypted ...
13 views

### Autokey Cipher Question [on hold]

you receive the message DQIXFQETXPPZZR Given that the ciphertext has been encrypted using an Autokey cipher with key k in the range 16 to 18, decipher the meassage. Thanks,
18 views

### Why does DSA require that a new $k$ be chosen and the algorithm restarted if $s=0$?

DSA is an algorithm used to generate a digital signature, which consists of a pair of values $(r,s)$. The algorithm computes $r$ first and then $s$. However, if we calculate $s=0$, it says to restart ...
32 views

### how to prove sequence y uphold golomb's third axiom

given $\{ x_k \}$ is a m-seq of order $n$, we define $\{ y_k \}$ to be a $m$ digits number: $$y_i=x_ix_{i+1}...x_{i+m-1}$$ for every integer $n \ge m \ge 1$ how can I show that $\{ y_k \}$ upholds ...
31 views

### How to use OpenSSL command line utility to encrypt data with encrypted key from public key?

I may not be asking the right question. I am fairly new to data encryption. I am currently being sent encrypted data that's stored as follows: [ [keysize] [key encrypted with public key] [ivsize] ...
90 views

### Key size for HMAC-SHA256 [duplicate]

After reading a bunch of past stack exchange posts like this one and RFCs 5869, 2104, and 4868 I felt comfortable that a 32-byte key was sufficient for HMAC-SHA256. However, I am implementing my code ...
30 views

### EC Schnorr signature: multiple standard?

I 'm working on some EC-Schnorr signature code. Reading various papers on that, it's seems EC-Schnorr is not standardized as well as ECDSA. For example, I found two main differences in two main ...