All Questions
3
votes
4answers
177 views
Is there a practical security difference between XXX-bit encryption?
I know I'm treading in dangerous waters asking this - my comprehension of cryptography math is sorely lacking. On the flip side it gives me massive admiration for what many of you are able to do.
...
0
votes
1answer
55 views
How to make a message into a polynomial on NTRU encryption?
How to make a message into a polynomial on NTRU encryption? for example how we can conver 'hello world' to polynomial...
i have read the converting operation on IEEE Std 1363.1- 2008, but i can't ...
0
votes
2answers
66 views
Voice Call Safety [closed]
When i was dealing with an assistant of my bank through mobile call, she asked me to insert my bank login code after a beep.
I was wondering if this procedure is secure against a Man In the Middle ...
1
vote
1answer
90 views
What's the difference between Trapdoor Functions and Encryption Functions?
From Wikipedia:
A trapdoor function is a function that is easy to compute in one
direction, yet believed to be difficult to compute in the opposite
direction (finding its inverse) without ...
1
vote
0answers
47 views
Predicate Encryption supporting disjunctions
I am not sure if I missed some subtlety in the definition of Attribute Hiding found in this paper on Predicate Encryption, but isn't it possible to construct a scheme for Predicate Encryption ...
8
votes
2answers
6k views
How does one attack a two-time pad (i.e. one time pad with key reuse)?
My question might appear the same as the question Taking advantage of one-time pad key reuse?, but actually I did read all the answers and none of them helped me with the details I need.
I am new to ...
5
votes
1answer
97 views
Using encryption schemes for identification
I've been researching how to implement a post-quantum SSL-like connection authentication, especially correct identification&authentization of the server/client. Because good post-quantum digital ...
4
votes
1answer
98 views
Client and server using same SSL certificate - any issues?
I'm working on software where multiple components will communicate with each other using SSL.
There would be one central component acting as a server, which would also require the clients to present ...
2
votes
2answers
84 views
How do I unpack the x and y values from the BITSTRING in a DER ECDSA public key?
In ASN.1, the X and Y values for a 256-bit elliptic curve key are stored as a single 66-byte ASN.1 BITSTRING. Are the values just the first and second half of this bitstring?
The private key is an ...
2
votes
0answers
97 views
Single-purpose symmetric encryption scheme for single files
I'm writing a simple password manager program that will encrypt/decrypt a single file (it's size will most likely stay under a few K). This is my initial file format design:
...
4
votes
1answer
162 views
Can SRP be used with Elliptic Curves?
I'm sure it can, because SRP (secure remote protocol) can be implemented everywhere where Diffie-Hellman works, but I need a proof to put this aspect into Wikipedia.
Edit: ok, can it be at least ...
4
votes
1answer
102 views
Which MAC scheme is quantum resistant?
will HMAC survive Grover algorithm ? if not then which MAC scheme provide post-quantum security ?
2
votes
1answer
207 views
Is AES-256 a post-quantum secure cipher or not?
We know Grover's algorithm speedup brute-force attacks two time faster in block ciphers (e.g brute-forcing 128 bit keys take $2^{64}$ operations not $2^{128}$).
That explains why we are using 256 bit ...
0
votes
2answers
51 views
How can two UProve token holders prove to a 3rd party that they aren't the same user?
Suppose I have two users who are issued two different UProve IDs. The Issuer has guaranteed that one UProve token bearer will never have more than one UProve token ID.
How can I use UProve to ...
16
votes
5answers
7k views
Taking advantage of one-time pad key reuse?
Suppose Alice wants to send encryptions (under a one-time pad) of $m_1$ and $m_2$ to Bob over a public channel. Alice and Bob have a shared key $k$; however, both messages are the same length as the ...
1
vote
2answers
84 views
It is reasonably safe to leave a SSH private key with a 30+ character passphrase public?
I'm curious about exploring uses for a distributing a single RSA private key with a passphrase instead of trying to secure the private key and distribute the public key. With the private key (and ...
1
vote
2answers
74 views
Can two rc4 encoded messages be XORed and decrypted if encrypted with the same key?
If I have the following:
E1 = RC4(M1, K);
E2 = RC4(M2, K);
If two different messages M1 and M2 are encrypted with the same key, K, can the key be recovered by ...
2
votes
2answers
111 views
one-time pad key related attack [duplicate]
In one-time pads we always say do not use same key twice to encrypt ASCII messages, but if we use a random key to XOR a random ...
6
votes
1answer
102 views
Is SpookyHash vulnerable to HashDoS?
Aumasson, Bernstein and Bosslet did an excellent job demonstrating fatal weaknesses in MurmurHash and CityHash, but what about SpookyHash?
My first uneducated guess is that it would be much harder to ...
2
votes
2answers
149 views
Why are RSA key sizes almost always a power of two?
I know that other bit sizes are possible, e.g. this HTTPS server seems to have a 9000 bit key https://www.ssllabs.com/ssltest/analyze.html?d=qqq.gg, but it's very rare that one sees a key not of size ...
7
votes
1answer
187 views
Alice trusts Bob only when Bob trusts Alice
some story first: Alice and Bob both have public/private key pairs. Now Bob wants Alice to sign his public key id. Alice agrees but only when Bob signs the public key id of her.
Is this something ...
2
votes
1answer
100 views
How to design a practical and secure MAC scheme?
I am sorry, but I need to introduce some concepts which are not directly related to cryptography to make myself clear, I hope I won't stun you with this ... (I'd rather explain it here than redirect ...
0
votes
0answers
76 views
How to choose between AES-CCM and AES-GCM for storage volume encryption
We are using the encryption built into Solaris 11 ZFS, which offers the choice between CCM (CBC counter mode) and GCM (Galois counter mode). What are the pros and cons of choosing each of these cipher ...
2
votes
1answer
70 views
Potential vulnerability in DH key selection - am I understanding this right?
I'm reading through a DH implementation, and I think I found a potential hole.
Public $p$ and $g$ values are properly selected.
A candidate secret value $\bar a$ is pseudo-randomly selected such ...
0
votes
1answer
156 views
What is the probability of breaking the AES algorithm?
I am doing a project which requires the encryption to be done using AES. Is it really possible (technically) to crack AES?
If yes, please tell me:
What is the probability of breaking AES?
How ...
2
votes
1answer
109 views
Is this hand cipher any more secure than the Vigenère cipher?
I know that inventing one's one crypto always sucks, but the problem is that hand ciphers are usually 1. very insecure 2. very slow. This is an attempt to make a relatively secure, keyable, and ...
2
votes
1answer
82 views
Is it feasible to break Diffie-Hellman key exchange when the implementation uses a poor-quality PRNG?
I've come across an implementation of DH in Java that uses the Random class to generate the secret integer value $a$, as shown in in Wikipedia's description of the ...
6
votes
1answer
129 views
Solving hard problems in $\mathbb Z_{p}^{*}$ when $\mathbb p$ is close to $\mathbb 2^{n}$
Suppose, for some security parameter $n$ you choose a prime $p$ such that $p = 2^n+c$ for some relatively small $|c| < 2^m << 2^n$. I have seen such primes being called Pseudo-Mersenne Primes ...
0
votes
1answer
231 views
SSTP MSCHAP-V2 Authentication before SSL or after SSL Session
So with the recent news that there's a lovely new tool to crack MSChapV2 packets.
So the question I have is on a SSTP Connection is the MSChapv2 handshake encrypted pre SSL setup or post. Obviously ...
-5
votes
1answer
39 views
AES ENCRYPTION ALGORITHM [closed]
What is the amount of decrease in the probability of decrypting a data encrypted using an AES algorithm? (That is by introducing each round out of ten whole rounds, how the probability of decryption ...
1
vote
1answer
93 views
which asymmetric cipher provide highest performance?
to get highest performance Which asymmetric cipher provide fastest encryption/decryption ? ECC or DH ? what key size is recommended today ?
3
votes
6answers
300 views
Where can I begin to study the math behind modern cryptography?
I've been studying (more like breathing and eating) crypto for almost a year now, implementing algorithms, reading books, studying code, etc. The deeper I go in, the more I realize there is; I feel ...
3
votes
1answer
74 views
How to use HMAC for large ciphertexts over TLS
HMAC used to secure chosen cipher-text attacks. if we are encrypting a large file (video) and sending it over TLS for decryption, how server can check MAC for ciphertext when we didn't sent whole of ...
2
votes
2answers
209 views
RSA private key format for Mega
I've been trying to reverse engineer Mega's (mega.co.nz) API calls. And stopped on the step where client needs to decrypt session id with provided RSA key. I can get key data, but I have no idea how ...
10
votes
2answers
267 views
Are safe primes $p=2^k \pm s$ with $s$ small less recommandable than others as a discrete log modulus?
I take the definition of safe prime as: a prime $p$ is safe when $(p-1)/2$ is prime.
Safe primes of appropriate size are the standard choice for the modulus of cryptosystems related to the discrete ...
4
votes
5answers
326 views
Any efficient text-based steganographic schemes?
While there are sophisticated and efficient steganographic schemes with images as cover available, I am yet ignorant of the existence of any fairly efficient and secure schemes with texts as cover. ...
1
vote
1answer
110 views
How to calculate y value from ((y*y) mod prime) efficiently
i am working ECC-224 bit. can any one tell me, how to calculate y value from ((y*y) mod prime) efficiently for large bit numbers.
0
votes
1answer
78 views
In which disciplinary kind can Cryptography be put?
Is it a multidisciplinary? an interdisciplinary? a cross-disciplinary? or a trans-disciplinary?
what are the basis put to describe each kind?
I mean how can we infer by which disciplinary field we can ...
3
votes
1answer
77 views
Any historical accounts of cryptanalysis of Jefferson's wheel cipher?
David Kahn in his book "The Codebreakers" wrote about Jefferson's wheel cipher, saying
that "To this day the Navy uses it" (the book was first published in 1967). Are there any historical accounts of ...
1
vote
2answers
121 views
Security of Deterministic Encryption Scheme
A deterministic encryption scheme is a cryptosystem which always produces the same ciphertext for a given plaintext and key, even over separate executions of the encryption algorithm.
Although we ...
3
votes
3answers
227 views
Export from US of crypto software with key-size > 56 bits still needs permission?
Elsewhere someone stated that he couldn't publish his crypto software on the Internet, because US Export Regulations require approval, if the key size is greater than 56 bits. I know that several ...
4
votes
4answers
195 views
What is the difference between a hash and a permutation?
As defined by Wikipedia a hash function is
[...] any algorithm or subroutine that maps large data sets of variable length to smaller data sets of a fixed length. For example, a person's name, ...
0
votes
2answers
211 views
Even passwords are vulnerable to hash collision attacks?
As stated in this page large documents hashed using md5 maybe vulnerable to collision attacks. My question is even passwords of 6-30 character are vulnerable to such hash collision attacks? If yes, is ...
0
votes
1answer
90 views
Sensible usecase for restricting special characters in passwords? [closed]
Please See Why Not Allow Special Characters In a Password on Security.
Several websites I've come across limit the allowed special characters for a password. My thought was, it should all be ...
0
votes
0answers
80 views
Secure modulus length for Diffie-Hellman
What is secure modulus length for modular exponentiation so that finding discrete log is computationaly impossible?
0
votes
1answer
36 views
reduces the coefficients of a modulo 3 on NTRU
i'm still don't understand about 'reduces the coefficients of a modulo 3' on NTRU tutorial
$a = f*e = 3 - 7X - 10X^2 - 11X^3 + 10X^4 + 7X^5 + 6X^6 + 7X^7 + 5X^8 - 3X^9 -7X^{10} \pmod{32}.$
Note ...
2
votes
2answers
156 views
How to efficiently generate a stream of independent, but biased random bits?
Usually, in cryptography, one is interested in debiasing a stream of independent (true) random bits, and several algorithms exist to do this. What about the converse? Let's assume I have a stream of ...
5
votes
2answers
481 views
HRNG for One Time Pad
I have just advanced to the last grade of high school (in Denmark). In this year, we all get to do one big project, where we can build/invent/create whatever we want to "solve a problem". As I study ...
4
votes
3answers
200 views
Comparison: complexity measures vs. security
Assume that you want to compare several cryptographic primitives (say, encryption schemes), and choose one. You need to consider several complexity measures, such as the key length, encryption time, ...
0
votes
3answers
127 views
File encryption with one keypair?
I'm working on a program that uses an ECC keypair in a (password protected) PKCS12 file (.pfx) to encrypt files. I like this method because I think it will be higher security (using ECDH to negotiate ...
