# All Questions

19,142 questions
11 views

### Hill cipher How to find unknown key with unknown size

How would you tackle the problem of finding the key(you don't know the lenght) to a Hill cipher while knowing only one 12 letter word of plaintext and its corresponding ciphertext? CONVERSATION has ...
11 views

### How to generate whitebox AES decryption algorithm and code, with existing WB-AES encryption code?

I can find several whitebox AES 128 implementations on Github, such as wbaes-1, wbaes-2, wbaes-3, etc. All of them are developed based on WB AES encryption. Ideally, most implementations include two ...
32 views

### What encryption shoud I use for single char encryption?

I'm very new to encryption and I wanted to know if it is secure or just possible to use encryption on single chars. I did some research, but nothing to clear and i'm a bit confused. The modes I think ...
11 views

388 views

### Distribution of safe primes generated using different techniques

Is there any difference in the distribution of safe primes generated by creating prime $q$ and testing $2q+1$ for primality, compared to generating a larger prime $p$ and testing $(p-1)/2$ instead? ...
24 views

### Are EdDSA algorithms encoded by ASN.1 DER standards?

Is it required, or widely practiced to encode a EdDSA signature as a ASN.1 Sequence? Why or why not? How should you encode a EdDSA signature? I cannot find mention of DER or ASN in the EdDSA RFC. ...
61 views

### How is the recommended NIST modulus for DLP chosen/calculated?

NIST recommends a 256-bit private key exponent for DLP with a 3072-bit modulus. From this answer it appears that the range of private key numbers is derived by calculating a prime modulus via $2⋅p$ ...
22 views

### Should I PGP encrypt using a publickey intended only for Certify?

I'm working with a publickey that does not include EncryptStorage or EncryptCommunication flags (see RFC4880 for flag reference). My question is, is it safe/appropriate to encrypt using this key? <...
36 views

### how are variable key sizes produced?

I am current learning the internal working of several Symmetric key Cryptographic algorithms, and came across DES and AES. DES takes in input a 64 bit key and AES-128 takes in input a 128 bit key ...
33 views

### I am participating on an international competition, my topic is Cryptography: The RSA Algorithm [on hold]

I am participating on an international video science competition. My topic is Cryptography: The RSA Algorithm. I would be more than happy to receive your feedback! Please take a look at it! It will ...
37 views

### Complete Attack on RLWE Key Exchange with reused keys, without signal leakage

I am studying your research paper "Complete Attack on RLWE Key Exchange with reused keys, without signal leakage" . On page number 21 to 28 of https://eprint.iacr.org/2017/1185.pdf , there is toy ...
34 views

### Are oracles needed in security proofs to prove that one problem is equivalent to the other?

I have seen a few security proofs where they show that solving one problem is equivalent to solving the other, via use of an oracle. For example, when proving that problem A is equivalent to problem ...
170 views

### How Will Quantum Computing Change Cryptography's Future?

Quantum computing is at the intersection of math, physics, and computer science and It seems enough complicated that only the large organizations could build algorithms and have their own quantum ...
93 views

### Was the Enigma's double stepping mechanism intentional?

It's sometimes refered to as the double stepping anomaly, so was it just a design flaw or was it put in place deliberately?
24 views

### Encrypt UDP packet with time-generated encryption key

I'd like you to help me solve a dilemma of mine. I am currently building a home automation from scratch for my next house. The basic gist of it is that I will send UDP packets over a local network. ...
79 views

### Prime number size and RSA decryption

Is there a former proof for why larger prime numbers make RSA securer? Maybe a theorem to show that it takes much more time to find out the private key if primes are larger?
28 views

### Pollard's Kangaroo— What is the failure probability (assuming random functions)?

I'm reading Pollard's paper on solving the discrete log problem, i.e. to find $x$ given $y = g^x$, where $g$ is a generator of the group. He has a Kangaroo Algorithm (page 4) which allows you, if you ...
25 views

### CRT to decrypt RSA [on hold]

How can the Chinese Remainder Theorem be used to decrypt RSA (or the public key) and find out the private key? If it is possible to do this with the CRT, then does the size of prime numbers used to ...
36 views

### Why adversary'' and challenger'' and what are typical roles of those?

I'm confused with words adversary and challenger, that are used in proof of security of some cryptosystems. For example, adversary and challenger appear in the formal definitions of IND-CPA, IND-CCA, ...
65 views

### Does this have a valid purpose [on hold]

2muchcoffee Just invented this. At the moment it is a pen and paper cipher. It is a cipher where you can store a file on a hard drive or U.SB. that has been encrypted by an unlimited number of ...
189 views

### Yarrow and weak cryptographic keys on macOS

Given that macOS uses Yarrow as a PRNG, and Yarrow is only capable of 160 bit outputs (/dev/random on macOS is actually Yarrow) are keys generated on macOS weaker than Linux? Even BSD has switched to ...
74 views

### Why does a padding block exist for ECB and CBC modes?

In ECB and CBC mode, the size of cipher text is more than the plain-text size by one padding block. From what I read, ECB does a simple encryption to each 64 bit block of a Plain text, and produces ...
42 views

### Chinese remainder theorem

Z/11Z[X] is the finite field P(2) = 4 P(3) = 3 P(5) = 7 How can I solve my congruence system with polynoms? I made my system of congruence like that : X = 2 [4] X = 3 [3] X = 5 [7] And it gives me ...
119 views

### Are one time pads still secure when using randomly generated words as the pad?

I was researching the US military's DIANA one-time-pad system and came across the following quote purportedly from a former US Special Forces soldier: Special Forces were one of (if not the only) ...
34 views

### What's the safest way to encrypt a messenger application?

How can I safely encrypt a messenger application that sends data over the Internet via TCP? I've already taken a look at Salsa20, but I don't know if that's a good algorithm to use for this. What ...
1k views

### Examples of protocols that are insecure when run concurrently

I was reading Canetti00 Universally Composable security paper. The first page of introduction says that there are some MPC protocols and Zero knowledge protocols that are insecure under concurrent ...
38 views

### Signature verification vs decryption?

I've found this explanation regarding signature verification but I still confused In the example in the picture, the sender sign the hash using his secret key. The output of signing produces a ...
38 views

### How to use openssl securely?

I don't want openssl to log my keys and passwords... but I don't use gpg as I need more manual control for my purpose. I also don't like gpg and would like to use openssl without logging. Does ...
40 views

### What does “simulatable” mean in security proofs?

I am reading a security proof in a paper as follows. Regarding the data confidentiality of users, all related public transcripts are simply the ciphertexts $\mathcal{C}_1,\ldots,\mathcal{C}_n$. The ...
40 views

### What does it imply if in RSA pow(m, e, n) is same as the m

So, Let's assume we have n which is made up of 2 strong primes which cannot be factored & e which is textbook value of e ...
27 views

### Mixing Cipher Lower Bounds

Let Z be a cipher system consisting of three m-sequence linear feedback shift registers (LFSR) of length 128 bits each which are assumed to be not cryptographically secure and the registers are seeded ...