1
vote
0answers
26 views

Is there a flaw in whole disk encryption vs volume or folder encryption? [duplicate]

My company just implemented whole disk encryption on all laptops (Symantec) and the concept seems flawed. Please correct me if I'm wrong, but if I have known file in plain text and that same file in ...
4
votes
1answer
154 views

Private set intersection, using a semi-trusted server

Alice has a set $S$ of words. Bob has a set $T$ of words. They want to compute the intersection $S \cap T$ of their words, with the help of a semi-trusted third party Trent. Trent runs a central ...
4
votes
1answer
209 views

Long-term data protection, storage of old encrypted traffic and quantum cryptocalipse

Tony Arcieri makes an interesting point in his Imperfect Forward Secrecy article which basically boils down to: large entities such as NSA are storing encrypted internet traffic, also what's to stop ...
1
vote
1answer
111 views

Is there any restriction in using lossless compression algorithms for huge key sizes?

I'm studying McEliece and Multivariate Public Key cryptographic systems. The main problem here is the huge key size. Is there any restriction in using lossless compression algorithms to fix this ...
2
votes
0answers
156 views

Sane implementations of Bitcoin cryptography routines w.r.t. side-channel attacks

Bitcoin uses SHA-256, Base58Check, ECDSA (Sep256k1) and RIPEMD-160 as the basis of its encryption (see this article for a short guide on how addresses are created). I would like to create an ...
5
votes
1answer
125 views

cryptographically good random elliptic curves?

After an answer here, about generate elliptic curves, I've start thinking about the algorithm. The mentioned algorithm will produce curves in the Weierstraß Reduced Form (WRF) over finite fields: ...
4
votes
1answer
196 views

a doubt in Rijndael's key expansion sizes

I've often heard/read that AES key sizes 256 & 192 would be weaker than 128 or not stronger as expected from the size increase, but I've never seen a proof. How does one proof the strength of a ...
2
votes
1answer
142 views

Reseeding a PRNG with the generated PRN

Would reseeding a PRNG with the PRN from the previous generation have any effects whatsoever on the quality of the generated numbers; if so, does this depend on the PRNG used, or are the effects ...
2
votes
1answer
99 views

What is the practical relevance of the wordsize when using a Hash?

I understand that the word size is the internal "working package size" below the block size of a cryptographic hash function (and a block cipher), as each block is broken into words an than processed ...
2
votes
0answers
52 views

Why the same characteristics cannot be used to recover all FEAL4 keys

I am trying to understand how differential Cryptanalysis works. Here I read how to use differential cryptoanalysis for cracking FEAL4 cipher. The big gotcha with this process is that you cannot ...
-1
votes
1answer
273 views

Understanding multiplication in the AES specification

I am reading through the AES specification and am not able to wrap my head around the multiplication definition (section 4.2). Sorry to refer to a spec but AES is the holy grail in crypto so I hope ...
1
vote
1answer
64 views

Using a hash with a constant key to create easily verifiable codes

I'll keep my question short. If I keep handing out different codes generated by this function, will it be trivial to figure out the secret key? ...
1
vote
2answers
79 views

Finding an x such that xP = (11,44) on an elliptic curve

Given the elliptic curve $$E:y^2 = x^3+17x+5 \mod 59$$ with point $P = (4,14)$, how do I find $x$ such that compute $x\cdot P = (11,44)$ Is there a mathematical method to compute $x$, or do I ...
7
votes
2answers
207 views

Why Victor must not know which tunnel Peggy chooses?

In the classic description of Zero Knowledge Proof of Knowledge, Victor must wait outside the entrance to the cave while Peggy goes to the fork and choose a side. It's only once Peggy has entered a ...
2
votes
0answers
71 views

Is ecryptfs safe after unmounting but before turning off the computer

I've read that one of the vulnerabilites of ecryptfs is leaks to swap memory, and that the solution is to encrypt swap. But even if swap is encrypted, it's still open until I reboot. I've also read in ...
2
votes
2answers
2k views

How to calculate the maximum output size for data encrypted with a RSA Private Key?

I have an an encryption algorithm I am working with that looks like this: prv_key_enc(sha1_hash(data)) Where, the RSA parameters are: RSA/ECB/PKCS1Padding 1024 ...
1
vote
1answer
331 views

Right usage of PBKDF2 and login system questions

I'm developing the login part of my application and I was asking myself how to do it right. My application stores some users' data server-side that must be inaccessible from us, so all the content ...
-1
votes
1answer
411 views

Number of possible keys in a Play fair cipher [duplicate]

So for the play fair case, the number of possible keys is : 26x26 = 676 possible keys But if we consider the repeated letters, how many unique keys will the play fair have? I mean how will ...
-1
votes
1answer
89 views

Adding “salt” to “doHash” function in Java [closed]

For one of my university projects I am being asked to "Improve the code to satisfy the pre-image resistance requirement." Basically the program is a basic encryption server system, and when I type a ...
3
votes
1answer
2k views

Who uses the RSA BSAFE library?

Who uses RSA's BSAFE library? Does anyone know what products use it, or have any statistics on how many end users use something that is built on BSAFE? Background: BSAFE is one of the oldest ...
4
votes
1answer
311 views

Can any one explain Circuit Privacy using fully homomorphic encryption from Gentry's thesis?

Craig Gentry's thesis talks about circuit privacy being straight forward from fully homomorphic encryption in the last chapter. Can somebody explain in simpler terms what that means ? I have read it ...
2
votes
1answer
266 views

Functional Encryption (for Non Experts)

I recently stumbled across "How to Run Turing Machines on Encrypted Data". Given that it's now possible to run turing machines on encrypted data, what open problems remain in the realm of Functional ...
3
votes
1answer
272 views

Rfc2898DeriveBytes - password length

Trying to find related answer for a long time, but not convinced yet. What I am trying is to encrypt using RijndaelManaged. To create Key, I am passing password, ...
1
vote
2answers
152 views

64 bit Elliptic Curve key?

For a simple proof of concept project i'm (attempting!) to do, i've started looking into openSSL elliptic curve cryptography. However instead of the standard key lengths, 160-512. I'm interested in ...
2
votes
1answer
844 views

Hill cipher cryptanalysis - known plaintext known key size

Hello I want to know how to go about this problem I know the plaintext "abcdef" and the ciphertext. The key size is 2. I really can't figure out how to find the key for decrypting and encrypting.
2
votes
1answer
2k views

Calculating the inverse modularity of the determinant for Hill cipher

I'm trying to decrypt a message encrypted with Hill Cipher, but I don't understand how to find the determinant so it solves the equation $det * 1/det = 1 mod 26$. The determinant for my key matrix is ...
3
votes
2answers
265 views

How to generate a random integer in interval $[1, 2^n-1]$ from random integer in interval $[0, 2^n-1]$?

For a project I am working on, I have access to a CSPRNG that outputs a random integer in the interval $[0, 2^n-1]$ for any integer $n$ greater than 0. I cannot use the zero values, so I have my RNG ...
1
vote
0answers
82 views

Does “use of SHA-256 in cryptography” imply use of SHA-256 both in HMAC and DH key exchange, assuming these are the only uses of hash in system? [closed]

I am beginner to Cryptography. And recently I came across the requirement like "use of SHA-256 in cryptography". Does "use of SHA-256 in cryptography" imply use of SHA-256 both in HMAC and DH key ...
2
votes
3answers
226 views
1
vote
0answers
140 views

Weil pairing implementation - low level programming language

I'm just started to studying elliptic curve cryptosystems. My one month-goal is to write a simple signature system based on the Weil-pairing. Some parts of it can be written without deeper ...
1
vote
2answers
332 views

why inverse in diffie-hellman protocol will not give same value?

Security of diffie hellman protocol is $K=g^{ab}$.if sender want to calculate value of $b$(given $a$) he can do $g^{{{ab}^b}^{-1}}$(where K=$g^{ab}$) which will give $g^{a}$ as we are cancelling value ...
2
votes
2answers
494 views

Certificateless cryptography

While reading "Certificateless Public Key Cryptography" by Author Sattam S. Al-Riyami and Kenneth G. Paterson, they have considered generation of private keys by a Key Generation Center (KGC). If the ...
1
vote
0answers
89 views

Is MITM possible after key exchange phase done successfully in RSA?

Is MITM attack theoretically possible after public/private key pair exchange is done successfully. Say Alice and Bob have genuine public keys of each other. Is MITM possible further during ...
1
vote
0answers
111 views

Which hardware-accelerated AES-GCM implementations support encryption in-place? [closed]

By encrypt in place I mean the following. Suppose I have an input plaintext of length L and I have also allocated an extra E bytes at the start and/or end of the buffer, with E << L. So the ...
4
votes
2answers
360 views

How can I implement the elliptic curve MOV attack myself?

I understand and have implemented elliptic curve signatures in Python without the use of libraries like Sage, and would like to implement the MOV attack against certain weak types of elliptic curves. ...
5
votes
3answers
2k views

Zero Knowledge Password Proof

I'm working on implementing a cryptographic system and I'm trying to understand the Zero Knowledge Password Proof concept. So here's some background: To generate a secret key I am: Doing an ECDH ...
1
vote
2answers
173 views

Tweakable encryption algorithms vs Key wrapping

I have read many articles about Key wrapping and tweakable cipher modes. However, I don't understand the main difference between them? What you recommend for Key storage and Key Archive.
1
vote
1answer
73 views

Secure Broadcast Channel

I've read a paper that says that one of the "assumptions" that it makes is secure broadcast. Why is this an assumption? Can't a broadcast channel be built with simple primitives--i.e. encrypt and sign ...
2
votes
1answer
252 views

Hashing fundamentals

I have some ideas floating around my head for exploring hashing functions, but I want to make sure what I think I know is actually true, before basing a house of cards on it :) Let’s start with some ...
1
vote
2answers
79 views

SHA-256 Wrong registers

I have a problem with my sha256 java implementation. The registers (a…h) are correct until j=24; ...
2
votes
2answers
349 views

What key exchange protocols give Forward-Secrecy resisting future progress?

I (wrongly) understood what I've been told as meaning DHE in TLS, PFS in IPSec do not provide Forward-Secrecy; and I'm told that common forward-secure key exchange protocols are restricted to ...
1
vote
0answers
50 views

Random numbers for Master Key and Key_block

Exploration through RFCs concludes that random numbers used in the creation of Master Key and Key Block(Key material for Encryption Key and Mac Secret) are from ServerHello.random and ...
3
votes
1answer
207 views

Unpredictability vs randomness

I'm experimenting with creating an entropy source for an environment where I have no hardware available and the language is very high level (executed in a virtual machine). I know it's not a good idea ...
2
votes
1answer
223 views

Fast modular reduction

I am looking at ways to speed up modular reduction for the polynomial $$2^{256}-2^{32}-2^9-2^8-2^7-2^6-2^4-1$$ I have read the paper "Generalized Mersenne numbers" by J.A. Solinas, but it does not ...
3
votes
0answers
231 views

Entropy of Androids motion-sensor data

My app on Android uses the built-in motion sensors to collect seed-data for the PRNG (java.security.SecureRandom) that is later to be used for key-generation. The user is told to shake the device so ...
1
vote
2answers
882 views

Is Dropbox's hashing method cryptographically secure?

Dropbox uses CRC32 and md5 to create a checksum of each 4 mb "block" as part of the their compression/file system. I suspect that Dropbox uses an additional cryptographic hash to check if there's a ...
0
votes
1answer
115 views

Prime factors of non-random keys

I have been working on a challenge i found on the internet. It is as follows: You've stumbled onto a significant vulnerability in a commonly used cryptographic library. It turns out that the ...
1
vote
1answer
69 views

Convincing “someone” on the (in)validity of DH tuple without revealing $u,v$

Is there a way of convincing someone on (in)validity of Diffie Hellman tuple $<g, g^u, g^v, g^{w}>$ without giving away $u,v$. or at least solve the Decisional Diffie Hellman Problem without ...
21
votes
2answers
3k views

Why is H(k||x) not a secure MAC construction?

If H(m) is a secure hash function, can't we implement a MAC using H(k||m)? However, it seems the more widely used MACs, such as NMAC and HMAC (both originally defined in Keying hash functions for ...
1
vote
1answer
114 views

Is script execution time a decent source of pseudorandom number generation?

This is for a PHP script for password generation. Naturally there are other things being calculated before the password is generated. But I figure the time it takes for the script to initialize and ...

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