4
votes
1answer
94 views

Backdoor in NIST elliptic curves

Let $E$ be an elliptic curve defined over a finite field $F_q$ with prime order $n$ and $P,Q \in E$ and $k$ be private key such that $kP=Q$. Since $n$ is prime, $E$ is isomorphic to $Z_n$. Suppose ...
0
votes
0answers
4 views

EmailAddress in x500name for CSR? [closed]

I would like to add EmailAddress to my PKCS10 CSR: .addRDN( BCStrictStyle.EmailAddress, emailAddr ) Why does the Bouncy/Spongey spec say the following?: ...
1
vote
1answer
14 views

One time Key Encapsulation Mechanism?

For KEM's, do you only exchange a private key once via the public key encryption and then do all further encryption with this private key, or is a fresh private key sent out with each message? The ...
-3
votes
0answers
49 views

How solid is this method of encryption? [closed]

Let's say your message is "This is a message." Now translate it into numbers. a=1 b=2 c=3 so on and so forth. Now take those numbers and turn them into three digits based on a randomly generated ...
4
votes
3answers
767 views

How can mega store my login details and still be secure?

I understand how Mega's encryption works. For a quick summary of all those in the future looking for an answer on this... here is how it works: Upon first signing up for an account you make a ...
5
votes
2answers
434 views

Security of tokenization of plain text conversations - cryptanalysis

I came across a marketing video here. They claim to perform AES encryption and tokenization of sensitive data, at the corporate gateway, before it leaves the company firewall destined for the public ...
0
votes
1answer
47 views

Best known attack

I always have listened the term best known attack but I have doubts respect to this term, becase there are several kinds of attacks for example structural attacks, inversion attacks. It is possible to ...
-3
votes
0answers
13 views

Can someone please decrypt “NUZGIEJX” using Vigenére [closed]

The key is "FUN". I just want to make sure I am doing it correctly.
3
votes
1answer
77 views

Why is padded RSA not CCA-secure?

Why is the padded RSA construction given in the picture not CCA secure?
0
votes
1answer
100 views

Is regular CTR mode vulnerable to any attacks?

Regular plain CTR mode, is it vulnerable to any attack? I plan to write a program to encrypt a drive with ctr mode. Would this be wise? Would AES be better? When I look at this diagram, it looks ...
-1
votes
1answer
49 views

Would the rotors in Enigma machines always advance by one position? Or was there a way to set this?

Before encrypting a letter the first rotor advances by one, right? So there could be a way, once the first rotor turns 26 times, make the second rotor advance two positions instead of one. Or three. ...
-2
votes
1answer
48 views

Affine Cipher - Greatest Common Divisor

Really simple question regarding the Affine Cipher. Can someone tell me how $3^{-1}$ is supposed to result in 9 in the following explanation below?
0
votes
2answers
136 views

How does a Hashing algorithm always result in a digest in a fixed size?

This question revolves around the Hashing Algorithm attribute that the resulting digest is always the same size (also known as Fixed Width). For example, whether you hash the word "hello", or 10gb ...
8
votes
5answers
329 views

Which cryptography technique does not increase the size of the plain data?

I want to encrypt some data(text/voice/video) but it is essential that the size of the cipher data remains the same as the plain data. Which techniques can I use, and how secure are these techniques ...
1
vote
2answers
1k views

What is the length field in SHA-512 padding?

If I am using SHA-512 on a message and need to determine the padding field and length field, how do I determine the length field? I think I understand the padding, but not the length field. For ...
14
votes
2answers
2k views

Can someone explain the ECB Penguin?

I've seen the ECB Penguin used to demonstrate why ECB is not a recommended method of encryption, but I do not understand how this translates to text or passwords. Aren't the people who create these ...
11
votes
2answers
2k views

Terminology: differences between the terms “pre-master secret”, “master secret”, “private key”, and “shared secret”?

Both crypto.SE and security.SE have excellent Q&As about how TLS generates session keys (I have linked some at the bottom). In reading these threads I'm having troubles with terminology since the ...
4
votes
1answer
83 views

Understanding Hellman's TMTO

I am trying to understand the basic TMTO by Diffie Hellman as described here. I am having trouble understanding this passage here: Hellman had the idea of storing the dictionary in the form of ...
1
vote
1answer
413 views

Blowfish ECB mode: Tools for known-plaintext attack?

I'm currently dealing with multiple blowfish-encrypted files that share the same key. All are encrypted using ECB mode judging from their appearance: I don't know what the key is but I know 64 ...
21
votes
2answers
2k views

Why is PuTTYgen-created RSA public exponent(e) not in {3,17,65537}?

As far as I know, RSA public exponent(e) should be one of {3,17,65537}. However, I found PuTTYgen-created RSA public exponent(e) is 0x25(37) by default,as follows, (PuTTYgen version: 0.66) I am ...
3
votes
1answer
143 views

Is finding collisions in a part-hash not often enough a bad problem?

My situation: I've been working now for a couple of months on my own unique hash function, I've changed it many times and had two main versions but I won't bore anyone with the details of my work; at ...
0
votes
1answer
53 views

Creating a message authentication scheme

I have such situation. I have a device like dongle. But it has certain limitations. For example, it can only have implemented encryption and decryption functionality. The availability of ciphers ...
3
votes
2answers
185 views

What is the difference between SHA-3(Keccak) and previous generation SHA algorithms?

SHA-1 and SHA-2 share the same structure and mathematical operation as their predecessors - SHA-0 and MD5. Both SHA-0 and MD5 have been broken. This is one of the main reasons why SHA-1 is considered ...
1
vote
0answers
49 views

What is th purpose of m and q in elliptic curve cryptography protocols?

In crypto protocols that contains calculus on elliptic curves I can often see $\dfrac{m}{q}$$Q$ where $m$ stands for order of EC points group and $q$ is the order of corresponding subgroup of $m$. $Q ...
1
vote
1answer
60 views

Why are there $q^2$ keys for each equivalence class in Pedersen-van Heyst Signature Scheme?

How do you know there are $q^2$ keys for each equivalence class in the Pedersen-van Heyst Signature Scheme? My textbook says this is "easy to see", however, I am not seeing it. Is it because in ...
1
vote
0answers
45 views

How to deal with collisions in Bitcoin addresses?

When creating a Bitcoin account, you need to issue a couple of private/public ECDSA-keys. Then, you derive your account address by taking a 160-bit hash (through sha-256 and ripemd) of the public key ...
0
votes
1answer
50 views

Key derivation using the main AES encryption key and some plain text

I am using AES 128 bit encryption in java. I have an encryption key and 10 digit plain text. I want to derive a key for HMAC using the AES encryption key and the 10 digit plain text. This plain text ...
1
vote
2answers
162 views

Different tools return different ciphertext value for equal input

I have a Luna G5 Safenet HSM and I want to encrypt a text file containing testtest with 3DES-ECB algorithm. So in the first step ...
3
votes
2answers
76 views

Why is it allowed to Generate Keys inside the game?

I am studying reductions to prove security of crypto systems. Generally "games" are used for the proofs. For example, the next image was extracted from the page 91 of the book Post-Quantum ...
0
votes
0answers
193 views

Simple two round feistel chiffre

I am currently learning for a exam in cryptgraphy. I now try to understand the Feistel Cipher with two rounds. I do not have any information on what the functions are actually doing. The following ...
1
vote
0answers
16 views

Sigma protocol: witness hiding

I am working on an assignment and I am stuck with the last part of proving witness hiding for the protocol. I have previously proved it is witness indistinguishable, and it has q (primer number ...
2
votes
0answers
169 views

What are the constraints on using GCM with a tag size of 96 and 128 bits

Say we want to use AES (or any other secure 128 bit block cipher) with GCM and a tag size of 96 or 128 bits. I'm assuming an AES key size of 128 bits and an IV size of 96 bits (the default). NIST ...
1
vote
1answer
49 views

Trying to udnerstand textbook sample solution

I am preparing for the final exam in my Data Security class so I am trying to read and understand the textbook's exercise questions. The sample solution at the end the textbook is more like a hint ...
14
votes
2answers
5k views

Is HMAC-MD5 considered secure for authenticating encrypted data?

I've read something to the effect that the HMAC construct is able to lessen the problem of collisions in the underlying hash. Does that mean that something like HMAC-MD5 still might be considered ...
1
vote
1answer
23 views

What is the starting point of Hellman's TMTO method?

I understand what is happening and how the endpoint is computed but I'm still a bit unsure of where "SP" (Staring Point) came from. Are the starting points, randomly selected keys from the key-space ...
1
vote
1answer
103 views

Is $f(f(x))$ a one way function?

I found from a book the following proof. Although I understand the initial construction, I don't understand the last sentence that proves the statement. Why $f(f(x))$, in the paper $h(h(x))$, is ...
0
votes
2answers
196 views

DES hardware implementation of substitution lookup table [ ReWorked ]

I'm a crypto enthusiastic and student of cryptography. I'm developing a project with other students titled "A hardware implementation of a DES cryptography for educational purposes", our idea was to ...
3
votes
1answer
72 views

4 x E = D in Simplified AES how it's possible?

Can anyone explain how it's possible through hexadecimal or Binary 4 x E= D
0
votes
1answer
229 views

Help with RSA-2048 crypto ransom virus [closed]

The RSA-2048 Crypto Ransom Virus has devastated me, I tried the backup method, the previous version, the Shadow Explorer, it deleted all my restore points, Its took out 5 HDs and my USB pen that ...
45
votes
1answer
3k views

Why does my SSH private key still work after changing some bytes in the file?

I (for a test) just randomly altered a private RSA key by opening it up in Vim and changing a few bytes. It is the private part of an SSH key pair used for logging in on a remote system. Puzzlingly, ...
4
votes
0answers
70 views

Secure entropy extractor for thermal noise collected from camera input?

I have read this paper (pdf) which talks about measuring the entropy of thermal noise collected from camera input. They estimate the minimum entropy at about 4 bits per pixel. Probably estimating 1 ...
0
votes
1answer
104 views

What is a branch number in the PAEQ algorithm?

I'm reading an article about authenticated encryption algorithm - PAEQ. It uses a permutation function AESQ, which has transormations from AES. And there is written about MegaSBoxes, which contain 4 ...
-1
votes
1answer
197 views

I homebrewed an algorithm. Is it secure?

This is a bit of a cross-posted question which I first asked at StackOverflow, however I was not satisfied with stackoverflow, so I came here for an in depth answer. I, as they say, "rolled my own ...
4
votes
3answers
125 views

Why are there $2^{56}$ possible DES keys when there are 64 key bits?

On forums I read DES has $2^{56}$ possible keys so it takes x times to brute force it with hardware x. But there are 64 total bits of which are 8 parity bits. But those parity bits are a ...
14
votes
3answers
2k views

Webcam random number generator

I have a question about random number generators. I have read from a real random number generator, based on a webcam ("randcam"). My problem is, that I do not really understand how the generation of ...
4
votes
2answers
153 views

How secure would hand ciphers be using a Block Cipher Mode?

I've been looking into different ciphers that require very minimal computation power (calculator, deck of cards, index cards and a pencil), i.e. hand ciphers. For the most part all methods typically ...
1
vote
1answer
52 views

TPM authorization Digest calculation

I am going through Steven Kinney's book; "Trusted Platform Module Basics", and pp 90 - 92 discuss how to calculate the authorization digest. He talks about 1H1, 2H1, 3H1, and 4H1 fields which I do not ...
-1
votes
1answer
43 views

Collision-Resistance Hash Function PRF

I am trying to solve the following question with an example/proof. The question is from Introduction to Modern Cryptography by Katz and Lindell. Any help would be appreciated.
2
votes
1answer
106 views

Doubling the block length of a given block cipher

IMHO the main essence of a Feistel cipher of block length $n$ is the working of a non-linear function $F$ that is applied to the two halves of the block of length $n/2$. Now suppose a certain block ...
3
votes
1answer
83 views

Known Plaintext Attack against 3-round SPECK48/96

I am attempting to break 3-round SPECK48/96 using a known-plaintext attack, provided with 10 PT-CT pairs. Here is a diagram: I have seemed to almost figure this out, but I cannot figure out how the ...

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