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Questions tagged [implementation]

Implementing a cipher or protocol is the process of taking it from its mathematical or algorithmic description and producing a working version, often in computer software or hardware. This tag should be used for any question discussing the various potential considerations and pitfalls of this process, for example padding.

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Implement Google Adiantum else where?

Google made the headlines with its new Adiantum encryption method, and i read (TechCrunch) that: In the meantime don’t expect any instant gains, but future low-power devices may offer better ...
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Does a masked look-up table prevent cache timing attacks?

When applying the boolean masking countermeasure to a cipher which uses an S-box $S$, a way to handle this nonlinear operation is to recompute a new S-box $S'$ such that $S'(x \oplus r_{in}) = S(x) \...
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Proxy decrypt algorithm in Extended Proxy-Assisted Attribute Based Encryption (ABE) Scheme

Context I'm trying to implement the Attribute-Based Encryption (ABE) scheme described in the paper - Extended Proxy-Assisted Approach: Achieving Revocable Fine-Grained Encryption of Cloud Data (Yang ...
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38 views

Starting stream cypher, first block (Salsa20)

I'm implementing Salsa20 in Rust for fun. I have the initial state (4x4 32-bit matrix) setup from the key, nonce, and stream position 0. I'm using the Wikipedia Salsa20 article as reference, and I'm ...
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83 views

Reducing the XOR's in Implementation Cost

Suppose that we want to implement the following equations in binary finite field. $$ \begin{array}{l}\tag{1} y_{{1}}=x_{{1}}\oplus x_{{2}}\oplus x_{{7}}\oplus x_{{8}},\\ y_{{2}}=x_{{1}}\oplus x_{{2}}\...
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Burmester Desmedt confused on the last step

I try to implement in code the traditional burmester desmedt algorithm for group key agreement: But I have the following question regarding the last step: $K=k_{i-1}^{nx_i}K_i^{n-1}K_i+1^{n-2}\dots ...
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42 views

Could you design something like a ring signature that uses website accounts instead of keys?

Ring signatures allow one to prove that you own a private key corresponding to a public key from a set of keys, without revealing which private key you control. This is useful if you are part of some ...
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79 views

Magic Number to calculate number of rounds for M-R in FIPS 186-4

In Fips 186-4, there is an algorithm in Appendix F (at page 117 in my copy of the 2013 version) to calculate the number of rounds of the Miller-Rabin primality test to random bases. Does anybody ...
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Implementations of GCM with 64-bit cipher

The paper The Galois/Counter Mode of Operation (GCM) describes mainly the 128-bit case, for use with 128-bit block ciphers such as AES. AES-GCM test vectors are available from NIST. The paper also ...
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104 views

Implementing randomness extractors

A randomness extractor is a function that takes an input sampled from high entropy distribution and outputs a value that is close to uniform distribution. It is slightly different from a PRG. PRGs ...
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WOTS+: Why does it XOR before running data through the hash function?

I'm implementing WOTS+ in a new language and I can't seem to wrap my head around the fact that WOTS+ XOR's their input with its mask right before hashing it. I tried to look for any reasoning but so ...
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ECDSA with common nounce?

I'm new to cryptography, and I've searching about ECDSA because I'm trying to solve a CTF. I've already check this site and Google, and I think I'm in the right path, but probably I am missing ...
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Choosing good entropy $g$ and $p$ for a classic Diffie-Hellman Key exchange

When selecting $g$ and $p$ for the Diffie-Hellman modular exponentiation: $ s= g^x \bmod p $ Which pairs of $g$ and $p$ are considered good nowadays, are recommended by bibliography? What I try ...
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Can I use NaCl's scalar multiplication functions for Diffie Hellman Key Agreement?

I want to create some software that performs diffie hellman group key agreement but I don't want to reinvent the wheel even if I know how it's done. So I came accross the NaCl library, especially the <...
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38 views

Gate count for Ring-LWE

In one of my recent research, I need to compare the number of gates needed in Ring-LWE encryption to AES in the circuit model. For AES we can find some estimation like this site, but for Ring-LWE we ...
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Why is this Trivium implementation working bytewise instead of bitwise?

I am currently looking into a Trivium implementation available in the FELICS framework. Parameters of the Trivium stream cipher: Key size: 80 bit IV size: 80 bit State size: 288 bit The Trivium ...
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Is one big file as secure as X small files with the same password?

Hello people of StackExchange. It's my first time asking and I know little about Cryptography, so be gentle. My problem can be simplified to this: I can create a 2GB Volume that contains 1GB of text ...
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Can the CRT speed-up Paillier decryption by more than a factor of two?

In the Pailler cryptosystem, decryption goes $m\gets\displaystyle\left\lfloor\frac {\left(c^\lambda\bmod n^2\right)-1}n\right\rfloor\mu\bmod n$ with $\mu<n$ being a part of the private key just ...
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Regular and Efficient doubling in $GF(2^n)$

A naive approach to compute a multiplication $a \cdot b$ in a Galois field of the form $GF(2^n)$ is the russian peasant algorithm. However, it does not run in constant time and therefore is not safe ...
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1answer
125 views

How to securely map messages to points on an elliptic curve

I'm implementing a demonstration hybrid cryptosystem in Python (FinCrypt, I know the name is bad) and I'm migrating over from my Weierstrass curve implementation, which was based off of this, to one ...
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Hardware AES: can we have a decryption implementation only?

I'm wondering if implementing only the AES decryption can reduce the hardware cost? And does anybody have some examples of the cost (speed, size) of hardware AES implementation? Thanks, Abaobaide
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Where can I find the description of SHA0 algorithm?

Where may I find the description and or pseudocode for the SHA0 algorithm. I am looking for something on these lines - HMAC RIPEMD. I have been implementing a few of those (HMAC, HOTP, TOTP and MD4, ...
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What should I change in my implementation to pass from a curve $y^2=x^3+1$ to $y^2=x^3+x$

I tried to change my implementation of pairing in curves $y^2 = x^3 + 1$ to use curves of the type $y^2 = x^3 + x$ but it didn't work. I thought the only thing I had to change in my code was the ...
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In a specific Paillier implementation, why is r prime?

I have a question about an implementation of the Paillier cryptosystem. In the description of Paillier above, encryption of a plaintext message $m$ on $\mathbb {Z}_{n^{2}}$, $0\leq m<n$, proceeds ...
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68 views

Non interactive Zero Knowledge Proof for Satisfiability of Pairing Product Equations

In the paper "Simulation-Sound NIZK Proofs for a Practical Language and Constant Size Group Signatures" from Groth, the section 6 describes a NIZK proof for pairing product equations. I only know ...
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Is there a consensus on what text encoding to use when hashing a string?

Let's suppose we are hashing a string input from the user via keyboard. A string can be interpreted in many different text encodings (ANSI, UTF-8, UTF-16 and many others). Based on what encoding is ...
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100 views

Pairing in implementation of a simple digital signature

I'm trying to implement in python the 1st scheme from the paper "Efficient Identity Based Signature Schemes Based on Pairings" by Hess to learn elliptic curve cryptography. It's a simple digital ...
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157 views

How to Calculate GE of Sbox?

How to count Gate Equivalent (GE) of Sbox used in block Cipher. For example how much area does the Sbox of Block Cipher Prince take? And How is it calculated?
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2answers
880 views

Why do algebraic proofs apply to cryptography?

How do we know that the number theoretic and algebraic results used in cryptography provide a perfect model for the behavior of integers as implemented in computers? Does there exist a bijection ...
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1answer
169 views

Right way to hash elliptic curve points into finite field

I would like to know how I can implement several hash functions : $H_1:\{0,1\}^* \rightarrow P $ with $P \in E(\mathbb{F}_q)$ and $H_2:P \rightarrow \mathbb{Z_q}^*$ And others where the ...
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Can you create asymmetrical encryption algorithm from symmetrical, without knowing how the algorithm works?

Let's imagine that we have some symmetrical encryption algorithm, that has only two functions: Encrypt(Data, Key) and ...
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301 views

Decode & Verify Base64urlUInt-encoded RS256 Public Key from Google

According to Google, to access the id_token it sends along with Access Tokens (for accessing their API), you must first validate the token using the RS256 Public Key available from this page. The ...
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Sigma protocol compiler?

Is there a well maintained, preferably documented, Sigma protocols compiler library? i.e. takes an abstraction of statements to prove, and outputs a cryptographic protocol between verifier and prover? ...
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About practical implementation of Ring-SIS/LWE Based Signature and IBE

In paper: Practical Implementation of Ring-SIS/LWE Based Signature and IBE, authors provided the source code for IBE. In the Extract algorithm, they said: $a \cdot x = u \bmod p$ but I can not ...
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296 views

ECDH over secp256k1 implementation

I'm using ECDH over secp256k1 in multiple languages, and I saw something a little weird in the rust library I use. After the point multiplication it changes y to <...
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129 views

UDP and AES with C++

I'm implementing different applications that will use UDP to exchange real-time data, thus a low impact on performance is very important. This system will not be connected to the Internet so I just ...
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How is pipelined DES different from sequential DES?

I implemented DES Coder in VHDL using ISE IDE by Xilinx in sequential architecture which was pretty easy and straightforward. Now my task is to do the same using pipelined architecture so that the ...
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Crypto implementations bits and bytes

Reading many papers in the Homomorphic Encryption domain and in Cryptography, a lot of schemes operate on bits as 1 and 0. If I wanted to implement a scheme, for example Gentry's FHE, would I have ...
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Implementation of ECC operations in BMR

I want to implement computing ECC operations(i.e multiplication) in BMR scheme (secure Multi-party computation) What is the best way to do it? I found Fairplay MPC - to allow BMR computation through ...
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1answer
276 views

Implementation details of the π step of the Keccak round function

In the official Keccak implementation overview, there is a section discussing different ways to organise the internal Keccak-f state -- namely section 1.2, Bit and byte numbering conventions -- and at ...
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How to thwart a cleartext message's size?

Here is a question I don't find addressed in my cryptography books: let's say Alice want to send Bob a message of length N. what is the proper way for Alice to hide N? I am thinking Alice should do ...
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Fermat's FFT based large integer multiplication

I was going through the documentation of GMP (https://gmplib.org/gmp-man-6.1.2.pdf), specially section 15.1.6 where they refer to the use of Fermat's style FFT. I tried to follow the reference but ...
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1answer
161 views

Wrong Miller's Weil Pairing implementation?

I tried to implement the Miller's Weil Pairing algorithm in python using the book "An introduction to mathematical cryptography" by Hoffstein, Pipher and Silverman. I tried my code with the example ...
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174 views

Why does TWINKLE use light instead of current?

TWINKLE is a device devised by Adi Shamir to optimize the sieving step of GNFS. It consists of a cylinder, at the bottom of which are LEDs corresponding to factor base primes which blink with ...
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How are multiple iterations of SHA-256 handled for longer inputs?

I wrote a python program to perform the SHA-256 function. It works just fine until I try to hash longer strings. If I hash (in HEX) ...
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Varying ECDH key output on different ECC implementations on the secp256k1 curve

Like the title says, I have used several implementations of ECDH, and I have found a discrepancy with libraries that wrap ...
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Using XL Algorithm to solve overdetermined systems, simple example required

Can someone give a small example of how the XL algorithm is used to solve an overdetermined system, with numbers and variables along with the steps if possible as apposed to just a general case? This ...
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How to compute this equation $(g^k)^\alpha\bmod p$

I have a question about implementation. How is an operation like this implemented? $$(g^k)^\alpha\bmod p$$ With all $g$, $k$, and $\alpha$ being large numbers. The thing that I find tricky is that ...