2
votes
0answers
10 views

How simple can the prp used in the Even-Mansour scheme be?

For example, in this question it is proposed to use AES with a fixed key as the permutation in a xor-permute-xor construction. In the paper linked in the answer, there is a proposal for a cipher that ...
2
votes
0answers
9 views

Computing cost for a trillionaire to compute GNFS in RFC 3766

RFC 3766, Section 4.1 discusses picking $n$ to achieve some target cost for employing the GNFS, i.e., $T$ is known and $N$ is unknown in the below equation: $$T = \kappa \cdot \exp{\left(c \cdot (\ln{...
0
votes
1answer
16 views

Symmetric encryption based on a mutable session key

I'm a newbie without pretension to ever be a master in this field :) However, after spent some hours in Google I couldn't find the right answer to a "simple" question. Let's imagine Alice wants to ...
1
vote
1answer
33 views

Where is the key into white-box AES cryptography?

After a initial study in white-box cryptography, specially arround the first article (Chow et. al.), I could understood each step to transform the tables of the AES into new ones and etc. If I ...
1
vote
1answer
107 views

justification for method to factorize n knowing RSA private exponent d

I know that knowing the private exponent $d$ corresponding to the private key $k_{pub}\langle n,e\rangle$ it is possible to efficiently factorize n. The procedure starts stating that: $ed -1 = s(p-1)...
3
votes
0answers
17 views

Incorrect answers to queries in Waters' IBE proof by Bellare and Ristenpart

In "Simulation without the artificial abort: Simplified proof and improved concrete security for Waters' IBE scheme", Bellare and Ristenpart present a new proof for Waters' IBE scheme that does not ...
-1
votes
0answers
30 views

Secure network protocol that can detect and adapt to attacks?

Is there any secure network protocol that can detect and adapt to attacks? For example: it would detect how hacker hacked it and then it can learn by itself and adjust itself and do encrypted ...
-6
votes
0answers
9 views

how write AES Inverse cipher key of 256 bit in verilog and inv mix column code in verilog .can any one have the verilog code [on hold]

how write AES inverse cipher key of 256 bit in VERILOG and inverse mix column code in VERILOG .can any one have the VERILOG code . can any body provide the VERILOG code
2
votes
0answers
28 views

Under which conditions would it be OK to use “H(pass||data)”?

I understand that the main motivation for HMAC is extension attacks. If data always has content-length either implicit in the app or even explicitly put into the hash, I get the impression that HMAC ...
-2
votes
2answers
59 views

Encrypting big numbers into small ones?

I'm new to cryptography and I am trying to figure out an equation that convert any big number to a smaller one and another one that reverse the operation to get the same big number again! The problem ...
0
votes
1answer
15 views

Does the Blowfish cipher work with OFB mode?

I'm trying to implement the Blowfish cipher in Output Feedback mode. OFB mode has two operations, XOR and the block cipher. XOR inputs two blocks of the same length and outputs one block of the ...
0
votes
4answers
29 views

Is XORing a random stream of bytes a secure way to obscure a file?

Long ago I created a very simple program that used the C library's rand method to generate bytes to XOR with the bytes of a file. This was a reversible (just run it through again) method to make a ...
0
votes
0answers
36 views

Is anyone using Half-Bit encryption? What is it used for now?

Long ago I learned about an encryption scheme which uses a random mask of bits which were "half on". I don't recall all the details, but basically, if a mask bit was a one, the input bit was passed ...
0
votes
0answers
15 views

AES/GCM Encrypt or decrypt from both Java and .NET [on hold]

New to encryption... I am trying to match an encrypt/decrypt routine created in Java with a .NET but I am getting a "The computed authentication tag did not match the input authentication tag" error ...
0
votes
1answer
34 views

Is “6 bit packed ASCII” an effective encoding to obscure text data?

I wrote a routine for a former employer that took the low six bits of ASCII text and "compressed" by cramming the bits together, so that 4 bytes reduced to 3. This had the advantage of automatically ...
2
votes
2answers
44 views

How can I resolve this basic MAC paradox I’m stumbling upon in my proof?

Suppose $S: K \times M \to T$ is a secure MAC. ($K$ = key space, $M$ = message space, $T = \{0,1\}^n$ = tag space.) $S$ being secure means that no matter what messages $m_1,...,m_q$ we throw at $S$ ...
3
votes
2answers
36 views

Are there some well-known crypto APIs that leak information?

Are there any well-known crypto APIs or libraries that leak or used to leak information (it can be the key or anything else)?
4
votes
1answer
48 views

SAT-Based Public Key Cryptosystem

I am researching post quantum cryptography and I've stumbled upon this article which presents a PKC with an np-complete (SAT) trapdoor. I was wondering if someone could help me understand the way the ...
0
votes
1answer
20 views

Calculating 3DES Key Check Value (KCV)

I am trying to verify a Triple DES Key Component generated by PC Crypto. The key portion is: E6F1081FEA4C402CC192B65DE367EC3E and the KCV value that should be ...
1
vote
4answers
86 views

Is this an effective obfuscation technique?

Long ago I created a simple program which obfuscated a file by taking the first byte, then XORing it with the second, taking the (original) 2nd byte and X-ORing with the 3rd, etc, down the line. The ...
4
votes
2answers
52 views

Order-Preserving Encryption (OPE) and leakage

I recently came across OPE and Order-Revealing Encryption (ORE), but I didn't exactly got the idea why they are important. What's exactly important about them? Are they actually used in practice? My ...
1
vote
2answers
98 views

Can a hash have more than one input?

From a definition stand point, can a hashing algorithm have more than one input, ex: $H(m_1, m_2, m_3)$? If not why are algorithms like bcrypt, scrypt and pbkdf2 referred to as password hashing ...
15
votes
2answers
3k views

Can Shannon's entropy be used to determine if a file is encrypted?

If we have to determine a file is encrypted or not, can we use Shannon's entropy algorithm on the file? As discussed here, the entropy (in bits per byte) being closer to 0 is considered as more ...
3
votes
1answer
54 views

How to meter and limit number of files encrypted?

First my apologies if this isn't the right forum for this but here's my problem : I have a black box that takes an input file and produces an output file. I want to sell this black box to a customer ...
0
votes
1answer
37 views

In which situation is HMAC mandatory rather than signature? [duplicate]

I’ve seen that the question has been asked already but this is still confusing to me. In a digital signature, Alice sends a message M and the ...
3
votes
2answers
22 views

HSM RNG - Compliance to FIPS 186-2

If the RNG of a HSM is said to be compliant to FIPS 140-2 (approved DRBG - SP 800-90 CTR mode) does also imply that it is compliant to FIPS 186-2 ?
0
votes
0answers
17 views

Homomorphic encryption implementation over circuits or assembly code [on hold]

I've looked at a few implementation of homomorphic encryption, such as HElib, but they only consider additions/multiplications and such. Is anyone aware of any implementation of homomorphic ...
0
votes
0answers
9 views

Entropy of Hash function [duplicate]

How is the entropy of the output of hash functions are defined? More specifically I saw in the paper https://eprint.iacr.org/2013/383.pdf Table 3 page 24. The entropy of challenge is mentioned which ...
3
votes
1answer
31 views

Proof for collision resistance on a block-based hash

I am designing an unkeyed hash based on the SIMON cipher. This is a follow up to “this” question. A quick summary: I have an ECC engine and the SIMON cipher in hardware, and it’s in an extremely ...
1
vote
1answer
44 views

Encoding an element in $r=r'||h(r')$ way

We consider a finite field $\mathbb{F}_p$, where $p$ is a large prime e.g. 256-bit. We have $b$ a fixed element of the field. We encode it as $b'=b||h(b)$, where $h(.)$ is a cryptographic hash ...
-1
votes
1answer
41 views

How to tell if an audio stream is encrypted or corrupted? [on hold]

Is the following stream encrypted or corrupted? I was on a call and then this happened: http://vocaroo.com/i/s0PlF2s8ULAU
-1
votes
0answers
34 views

How we compute distance after lshashing? [on hold]

If we use an lsh function under l2 distance (hw,b(x)= ⌊ (wTx)/r ⌋ where w is a d-dimensional vector with entries chosen independently from a 2-stable distribution, r is a positive real number) or ...
1
vote
0answers
23 views

Proof that two signatures are done with the same short bases

My question is regarding lattice based signatures. Each lattice can have multiple short (secret) bases. Is it possible to proof in zero knowledge that two signatures on a fixed lattice have been ...
1
vote
0answers
17 views

What is the exact algorithm and functions of the 4 way handshake?

I have to make a detailed diagram of the 4 way handshake and formulas for its functions so I need to know the exact process behind it. Like precisely what functions are used in it? I have been trying ...
5
votes
1answer
186 views

How should I read these three-dimensional (pseudo)random-generated numbers representations?

Visiting this site: http://lcamtuf.coredump.cx/oldtcp/tcpseq.html#phase I found graphical representations of random-generated sequence numbers, but I can't figure out how to interprete the plots. ...
0
votes
1answer
37 views

A5/2: Ciphertext Only Attack

A5/2 could be attacked with cipher-text only, using the Error Correction Code, in order to retrieve the session key. For the purpose of simplicity suppose that the error correction code copy the ...
12
votes
4answers
3k views

Which public key cryptosystems are not based on number theory?

Are there any public key cryptographic systems whose hardness assumptions don't involve number theoretic problems?
-2
votes
0answers
46 views

any post-shannon symmetric ciphers?

As far as I understand block ciphers use only simple operations to ensure good enough confusion and diffusion levels. meaning there is no math in it. "breaking a good cipher should require as much ...
4
votes
0answers
45 views

Does changing the order of the steps within a round affect the security of AES?

I was trying to understand the internal structure of AES (Advanced Encryption Standard) Standard order of steps within a round: Substitute Bytes Shift Rows Mix Columns Add Round Key Substitute ...
3
votes
1answer
44 views

What do the last chunks of the output string of Scrypt contain?

When you use scrypt to hash a string, it will generate something like: ...
0
votes
1answer
31 views

Why is symmetric lightweight crypto only about block ciphers and not about stream ciphers?

Why is symmetric lightweight cryptography only about block ciphers and not about stream ciphers? AFAIK stream cipher implementations cost at least three times less than block cipher ones?
1
vote
1answer
33 views

In Paillier homomorphism how do you substract?

I'm trying to learn homomorphism so the problem may also be in my code (which I will include). I want to compute $a - b$ where $a$ is bigger then $b$. In order to do this I tried to compute $\frac{a}...
1
vote
1answer
30 views

“NP-complete” authentication systems

Are there any symmetric authentication systems based on the hardness of an NP-complete problem? I understand that it doesn't really matter, since NP-completeness is about the worst case, and in crypto ...
1
vote
1answer
38 views

Rotating password with PBKDF2

Crypto is hard. Thank you for helping me learn. My encryption scheme currently looks like this: Salt is stored out in the open Secret is the user's password, known only to them EncKey||AuthKey = ...
-2
votes
0answers
28 views

Signing and hashing a new file detected in a folder [on hold]

I'd like to sign a file in a folder after detection. I'd also like to save a hash over the file to a text file. Thanks in advance!
6
votes
2answers
361 views

We can obtain “absolutely perfect CONFIDENTIALITY” using the one-time pad. Is there such a thing as “absolutely perfect INTEGRITY”? [duplicate]

The OTP (one-time pad) gives us perfect secrecy. This is the very best confidentiality available in this universe. (Although it does require large keys, which is beside the point of this question). ...
1
vote
0answers
44 views

Feasible attacks on ECRSA cryptosystem

In ECRSA cryptosystem, I want to know the feasible attacks. For illustrations we have two prime $p$ and $q$ such that $p \equiv 2 \pmod 3$, $q \equiv 2 \pmod 3$ and generate key pair as follows: $$n = ...
0
votes
1answer
23 views

In Paillier homomorphism, how do you deal with bit length? [on hold]

I'm trying to figure out homomorphic encryption and would like to multiply two paillier encrypted numbers. Like so: [a].[b]=[a+b] To try this I got this Paillier.java and tried the following: <...
5
votes
1answer
123 views

How can I instantiate a generalized hash function?

I've come across a bunch of "strange" hash function notations, such as the following ones and now I don't know how to choose / instantiate them. Can you please explain me what this notation means and ...
3
votes
2answers
49 views

SHA-3 maximal number of zeros (Padding)

What is the maximum number of zeros, which are appended at the input- padding in messages? How large must the message be for this?

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