# All Questions

336 views

### Montgomery Reduction

I'm taking a hardware cryptography class and working on a problem that focuses on Montgomery Reduction. So by definition: Computing a x b (mod N) Pick R, s.t. R > N, gcd (R,N) = 1 Compute N^-1 ...
46 views

### Cache Attacks on Cloud Infrastructures

I read something about cache attacks like this: Enter KSM (Kernel SamePage Merging). KSM enables the kernel to examine two or more already running programs and compare their memory. If any memory ...
516 views

### nonce of AES-GCM in SSL

It seems that the nonce of AES-GCM in SSL has 3 parts: salt, 4 bytes, generated in handshake, not changed in whole session nonce_explicit, 8 bytes, chosen by the sender and carried in each SSL ...
45 views

I was reading about HMAC and why it is crucial to avoid security issues with normal prepending / appending the secret k to a message (issues due to merkel damagard construction). I am not familiar ...
115 views

### Meaning of Signature hash algorithm field in certificate

I'd like to understand what is the meaning of this field, especially considering that when calling a crypto library to sign data the digest method is specified by the caller. For example, this simple ...
78 views

### Standards/RFCs for non-Diffie-Hellman perfect forward secrecy?

Some time has passed since PFS introduction and we now have secure&proven asymmetric ciphers that can generate strong keys very efficiently (elliptic RSA variants and/or QD-Mceliece can generate ...
66 views

### Zero knowledge proof relation + number is binary

I want to develop a ZKPK for the following problem: $$Y=g_0^{r_Y} \prod_{i=1}^n g_i^{s_i}$$ and $$Z=h_0^{r_Z} \prod_{i=1}^n h_i^{s_i}$$ I want to proof knowledge of $r_Y,r_Z$ and $s_i$ which I have ...
87 views

### Generate hash value using public key along with message

I was trying to understand one way signature chaining on message by saxena and soh. As the message is passed from one user to other, every user can combine their signature to create one single ...
148 views

### BER or DER X9.62 ECDSA signature

The signature format for ECDSA signatures can be encoded using ASN.1 integers according to X9.62 or it can comprise of two integers with the same size as the key size. In case the X9.62 format is ...
123 views

### Solve a problem, thought it was hash length extension, hours later, am I wrong?

Here is my situation. I'm working with an application for which uses hashing to authenticate data. I have a string, which is hashed. It is, like in a hash length extension attack, H(key:known_value) ...
136 views

### Is there a need to encrypt data when send over https? [closed]

I was monitoring web traffic from my Android mobile using Man in the middle proxy. I installed certificate signed from my server in my mobile and I could see all applications sending sensitive ...
82 views

### In what countries am I now allowed to talk about technical details of cryptography? [closed]

I hope this is the correct place to post this, otherwise I'm sorry. The OpenSSL Legality section states: OR EVEN JUST COMMUNICATING TECHNICAL DETAILS ABOUT CRYPTOGRAPHY SOFTWARE IS ILLEGAL IN ...
38 views

### RSA, proof of correct work, if p is not a prime number [duplicate]

Is there any proof of correct work of RSA algorithm, if p is not a prime number? For example: n = p*q, p = p1*p2, where p1 and p2 are primes. Edit: I found that it's called Multiprime RSA, but i ...
46 views

### Zero knowledge of two factor

Here I overconfident in myself state that I can show, that n has two factors. This is not completely true, can possibly show $n$ is composite - prover generates RSA key with modulo $n$, and gives $e$ ...
39 views

### Security of simple Skein PBKDF mentioned in the paper

From the Skein 1.3 paper section 4.8, Skein as a Password-Based Key Derivation Function (PBKDF), it mentions the following as a simple PBKDF (S = seed and P = password): An even simpler PBKDF is ...
90 views

### Construct rainbow table to break DES

I'm facing a project where I need to build a rainbow table to break DES. I've already collected information about Hellman, DP, rainbow table method. Finally, I chose the rainbow table approach. I've ...
29 views

### Is RSA-OAEP secure when e=3? [duplicate]

Is RSA-OAEP secure when the exponent is equal to 3?
62 views

### Statistical saturation attack on block ciphers [duplicate]

I was wondering if anyone around here could give me some explanation on this type of attacks. Pretty much the only thing that I could find is this What I really need is basic explanation of the ...
50 views

### Encryption with a known plaintext

I'm building an application where users can be a part of groups, and can obtain and distribute URLs from the group page that allow anyone who clicks on them to join said group. Groups should not ...
33 views

### WPA and WPS: connection method [closed]

Do clients use WPS every time when they connect to a WPS-enabled AP? Or maybe they do it just the first time and then they switch to a normal WPA/WPA2 key exchange? If the latter, it's possible for ...
194 views

### FileVault AES-XTS decryption with cipher text that's missing a part

My mac was recently upgraded to OS X Yosemite and FileVault2 full disk encryption was turned on. Encryption finished, but things went horribly wrong and key parts of the disk are filled with all 0s ...
110 views

### Beginner question about secure communication with one user using DES

I am currently learning about encryption and I was asked a question: If a customer only had a DES system how could I secure messages as DES is not secure. I was researching this and I came across a ...
37 views

### What is the difference between any secret sharing scheme and arithmetic secret sharing scheme

It looks like that only difference between two of them the variables. But it does not make sense for me and I could not find exact definition of arithmetic secret sharing scheme. I mean what exactly ...
31 views

81 views

### Exploration of Blum Micali Security By Seed Size

I'm new to cryptography and am most intrigued by mathematically based pseudo random number generators. With reference to the Blum Micali algorithm: $X_{i+1} = G^{X_i} \bmod P$ can security be ...
232 views

### ASN.1 encoding off RSASSA-PSS default parameters

I am not totally sure the question belongs to crypto and not stackoverflow but nevertheless... The problem is the encoding of the RSASSA-PSS default algorithm identifier parameters in an X509 ...
155 views

### Montgomery Algorithm

I'm trying to undestand how it works and how to implement the algo described in this paper. The paper shows a methods to compute a modular multiplication where it is used multiplier with a resolution ...
152 views

### Split 32-bit LFSR into two 16-bit LFSR which xor to same sequence [duplicate]

Today I was thinking about exactly this. Is it possible, for a 32-bit LFSR e.g. ...
56 views

### Is there a way to “shorten” a Merkle chain?

If I have a Merkle chain of 3 items, is it possible to create a zero knowledge proof of the existance of a correct chain between hash 1 and hash 3? Editing to clarify (Thanks Ricky), what I mean my a ...
60 views

### Obliviously computing the Least common multiple of two poylnomials

Consider I have two polynomials $f_1$ and $f_2$ of the same degree. I want to secure them (using any kind of encryption except FHE) and outsource them to an untrusted server. I want him to compute the ...
I've heard in some lecture that the weak keys in DES implies the existence of $2^{32}$ fixed points in the algorithm, i.e. that $DES_k(x)=x$ for $2^{32}$ such $x$'s. I couldn't find anything about ...