-1
votes
0answers
30 views

rngtest results interpretation [on hold]

With: rng-tools version 2-unofficial-mt.14-1 Tested this C++ code: ...
0
votes
1answer
33 views

Question on Miller's algorithm (change the input m)

From the book titled " An Introduction to Mathematical Cryptography" (Chapter 5,page 322), we know that the miller's algorithm returns a function $f_P$ whose divisor satisfies $$div(f_P) ...
2
votes
1answer
49 views

Question about keyed hash functions

Maybe the answer to my question is obvious, but I have doubt... I have noticed that hash functions are studied in two forms, keyed hash functions or unkeyed. In general, lecture notes present hash ...
2
votes
2answers
700 views

I hashed my bag and in it I put… “Is there a hash for unordered items?”

(By items I mean hashable objects.) As an example (with obviously way too short hashes for readability), say I packed my bag and in it I put a shovel (hashed to ...
0
votes
1answer
86 views

Why is a Feistel network bijective?

EDIT: Fixed for clarity of intention I was reading "The FFX Mode of Operation for Format-Preserving Encryption" when I came across Figure 1 (see below). It's obvious why it's reversible (top-down ...
0
votes
1answer
135 views

security proof in pairing based cryptography

Let : $G_{0}$ and $G_{1}$ be two multiplicative cyclic groups of prime order $p$. $g$ is a generator of $G_{0}$ and $e$ is a bilinear map, $e : G0 ร— G0 โ†’ G1.$ $๐ถ_{1} = ๐‘”^{๐›ฝ๐‘ _{1}} $, $ ๐ถ_{2} = ...
0
votes
1answer
74 views

Key Confirmation Attack [Key Distribution Center (KDC)]

Okay this is how I understood it according to this: Alice $A$ establishes a connection to $KDC$ and prepares for session key Exchange $k_{ses}$ $A$ encrypts the request with her key $k_A(A, B)$ ...
0
votes
2answers
181 views

Cryptosystems used to generate public key certificate

Where can we find the cryptosystems used to generate public key certificate? Are the cryptosystems under the signature algorithm and signature hash algorithm? Do I need to analyze the packets ...
2
votes
0answers
36 views

Logjam-style attack on Factoring?

We're all aware of the Logjam attack, which is known as "FREAK on discrete logarithms". Now the attack works by doing a large pre-computation step, which needs only to be done once per field and then ...
4
votes
1answer
53 views

Parallel authentication of encrypted data. What AE type to choose?

I've got a system with a slow data transfer channel. Transferring a message through several channels does increase the transfer speed significatnly. AES-CBC+HMAC is good except that verifying the MAC ...
2
votes
1answer
33 views

Meaning of pseudocode “$(C, S):=$”

I've seen pseudocode of this form in the Montgomery Multiplication related theses: $(C, S) := a[j]*b[0]+C$. What's the meaning of "$(C, S):=$", or what is the real code that converted from this ...
2
votes
3answers
70 views

Reasons for components of AES

I started reading "Cryptography: theory and practice" by Stinson, and I am trying to understand the reason behind the choices for the different components of AES since they seem quite arbitrary. In ...
5
votes
2answers
140 views

Is standardizing a modified AES a good idea?

"Recently" the Ukraine standardized a new block cipher Kalyna, which according to the abstract of this paper (warning: the paper contains a lot of test-vectors) is basically a modified version of AES. ...
1
vote
1answer
35 views

Does anyone still use BAN or GNY logic in practice?

I want to implement a simple protocol, and I'd like to verify it through BAN or GNY logic. I would assume that if these logics are still used that there would be some programs available that would ...
5
votes
4answers
2k views

Is a book cipher provably secure?

I've seen ciphers (usually in spy drama shows) that involve taking a book and writing down an index to individual characters. Essentially it's a keyed substitution cipher, where the key is the name ...
1
vote
1answer
37 views

Does XTS provide random write access?

I'm trying to find a sufficient encryption mode that supports random read and write access. It seems like XTS is a perfect fit, since in my use case authentication and integrity insurance are handled ...
6
votes
3answers
300 views

Can passwords be stored securely so that a similarity comparison can be made?

On the Pro Webmasters StackExchange site, someone asked a question about a webapp (in this case cPanel) that refused to allow a password change because it was too similar to a previous password. I ...
0
votes
1answer
55 views

The encryption scheme is secure?

I have a scheme and I don't know that this scheme is semantic security or not. -Secret keys $\{s_1,s_2, x_1,x_2\}$ and public parameter $p$ (large prime number) -Encryption E(m): $C_1 = s_1m + x_1k ...
1
vote
1answer
108 views
+50

How broken is a xor of two multiply with carry generators?

How broken is a xor of two LCGs? How Brittle Are LCG-Cracking Techniques? Based on the above two questions, I have simply one additional question: how broken is a XOR of two 64-bit multiply with ...
0
votes
0answers
20 views

RSA: If I sign the same digest with same key twice, will the signatures be identical? [duplicate]

If I don't have public keys to verify the signature, can I use this to discover that two signing services are using the same key? Can you send a reference?
1
vote
1answer
18 views

What is a man-in-the-middle attack (for instance in Diffie-Hellman)?

I'm new to cryptography and I just started learning about the Diffie-Hellman key agreement. I read that this system is vulnerable to a man-in-the-middle attack when used alone. What kind of attack is ...
0
votes
1answer
79 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 ...
4
votes
1answer
195 views

Will hashing over and over eventually give the same hash?

There are many cases in maths where doing the same thing over and over again will bring you closer to a value. Derivation of polynomials is the striking example: no matter what you start with, you end ...
5
votes
2answers
275 views

Encryption of small messages

Some time ago, I asked how to encrypt small messages like e.g., four decimal digit numbers (banking PINs). I've got my answer, but also a warning like it makes no sense as it's easy to guess: Even ...
2
votes
1answer
34 views

Why should the input value on a DPA attack be non-constant?

I actually was wondering if anyone could help me out with the following problem: Let's assume we are attacking the first SubBytes() operation on AES with the help ...
1
vote
3answers
53 views

Is this client-side password hash scheme secure?

I want to build an app that uses client-side encryption for storing encrypted data on the server. A user-specific master key would be used, so to easily share it between devices a encrypted version of ...
3
votes
2answers
66 views

Does authenticated encryption add any protection to a signed digital envelope?

The general scenario of hybrid encryption is to use public key cryptography for the exchange of a one time session key that can be used for the encryption of the plaintext with a symmetric encryption ...
9
votes
4answers
2k views

Is the one-time-pad a secure system according to modern definitions?

Occasionally I hear people say that one-time pads are "useless" or even "broken". "modern cryptography knows more security definitions, under some of which the one-time pad is completely ...
6
votes
6answers
2k views

Relative security of a Vigenère cipher

Within a closed computer network, I am ciphering some plaintext data as an added security measure. This is below several other layers of protection. For various technical reasons, I am restricted to ...
3
votes
1answer
71 views

How often does RSA-OAEP have a leading zero?

We are working with a third party vendor who is very tight lipped about their security protocols, and one of our customers who used this vendor's products is claiming that approximately one in every ...
3
votes
3answers
639 views

Creating a license system based on asymmetric encryption (RSA or ECDSA)

Iโ€™ve spent a couple of days researching the topic of creating a license system for my desktop software. While I fully understand that thereโ€™s no perfect copy protection, this approach seems to have ...
3
votes
3answers
230 views

A specific way for deniable encryption

I read the summary of deniable encryption on wikipedia: https://en.wikipedia.org/wiki/Deniable_encryption Then I read a question, by doom123 on security.SE: ...
1
vote
1answer
35 views

Pseudo Random Function

The definition of pseudo randomness that leads to pseudo random function talks about indistingishability of a key-ed function and a random function. i.e. The key-ed function family $\{F_k\}$ is PRF ...
2
votes
5answers
3k views

“123456” and “password” as crack standards

I know that when we encrypt, we use standard encryption technologies and to store data it's often stored as a hash. By encrypting a common password, for example "password" using ...
1
vote
3answers
74 views

Why not put MAC in fixed position and cover padding for MAC-then-encrypt?

The biggest problem with using MtE with a mode where it's known to be secure (CBC) is with the padding, where you can't retrieve the authentication until you know where it is by looking at the padding ...
1
vote
1answer
193 views

Suggestion : CRC vs SHA1

I need some suggestions about the use of the CRC in my application. I need to be sure about the BIOS run by the CPU. I have a FPGA between the BIOS flash and the CPU that sniff every read performed by ...
2
votes
3answers
50 views

Frequency tables for HTML page source

Are there online resources with an ASCII character frequency table for HTML? There's tons of them for english, but I can't seem to find one for page source. I know that this is something that's ...
0
votes
0answers
28 views

what do you mean by cost in encryption? [on hold]

What do you generally mean by cost of an encryption algorithm? how are they computed and how to compare the cost of two encryption algorithms?
-1
votes
1answer
52 views

Theoretical Mathematics & Cryptography [closed]

I read in Bruce Schneier's book ,"Applied Cryptography", that cryptographers need to study theoretical mathematics in order to be good at their job. Why is that?
4
votes
3answers
153 views

Why aren't zero-knowledge proofs used for authentication in practice?

I read on Wikipedia that zero-knowledge proofs are not used for authentication in practice. Instead (I think) the server is entrusted with seeing a password in plaintext form, which it should then add ...
1
vote
3answers
146 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. ...
139
votes
8answers
30k views

Should we MAC-then-encrypt or encrypt-then-MAC?

Most of the time, when some data must be encrypted, it must also be protected with a MAC, because encryption protects only against passive attackers. There are some nifty encryption modes which ...
0
votes
0answers
10 views

Creating disk image of encrypted disk [migrated]

I'm Fedora 21 user for some time and I'd like to create disk image to escape installing everything over again when something fails. I have encrypted storage and that fact makes me wonder. How do I do ...
0
votes
1answer
67 views

ElGamal scheme attack when one message is known and ciphertexts are intercepted

Let $G$ be a finite cyclic group of order $p$ and let $pk = (g, h=g^a)$ and $sk=(g,a)$ be Bob's ElGamal public/secret key pair in $G$. To encrypt a message $m$, a random number $r$ is selected and a ...
0
votes
0answers
35 views

Cryptographic Disk wiping with quantum random data?

I was thinking about using 4 Quantum Random Number Generators working at the same time to create a secure disk wiping system. Basically feed the random bits into to an approved DRBG then through an ...
3
votes
1answer
83 views

Simulation aborted because the adversary doesn't use the random oracle

I'm trying to construct a proof for an encryption scheme in the Random Oracle model. This encryption scheme is like a PKE scheme but with an additional function that kind of "alters" ciphertexts ...
4
votes
1answer
592 views

Understanding elliptic curve encryption

I'm having a hard time understanding the elliptic curve encryption. One thing thing I don't understand is listing all the points on the curve mod p. Suppose I have the following elliptic curve: $y^2 = ...
12
votes
3answers
929 views

What is a Non-Interactive Zero Knowledge Proof?

I understand the concept of a Zero Knowledge Proof thanks to the easy to understand analogy of Alibaba's cave. However, this seems to require interaction between the verifier and the other party. I ...
0
votes
1answer
58 views

RSA function over $Z_t^{*}$ where $t$ is prime

RSA function is defined over $Z_N^{*}$ where $N=pq$ with $p,q$ primes. A public key is a pair $(N,e)$ and a private key is $(N,d)$ where $d=e^{-1} \mod \phi(N)$. Assume that RSA function is defined ...
0
votes
1answer
49 views

Interesting malleability property of Goldwasser-Micali PKC

GM is a cryptosystem with a modulus $N = pq$ ($p$, $q$ prime) and quadratic nonresidue $r \in (\Bbb Z / N\Bbb Z)^*$ as the public key. You can see the details on Wikipedia. Anyway, let's say that $N ...

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