# Questions tagged [optimization]

Questions about problems that entail selecting the best element from some set of available alternatives, and methods to solve them.

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### Is there any bijective obfuscation scheme which maintains a byte order (e.g. sorted) or does so after not too many trials? (for 128bit = 16 byte)

We have given 16 bytes and apply some order to them. For example sorting them by their absolute value. We want to obfuscate them as best as possible while maintaining their order. That means if we ...
• 453
1 vote
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### OPRF based on symmetric encryption

We need to use OPRF(oblivious pseudo random function) on very large sets. Unfortunately most of algorithms use elliptic curves and so this algorithms are very slow. Does exist some relaxation of oprf(...
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### What is the fastest stable 128-bit non-cryptographic hash function?

I need a stable 128-bit hash function which is extremely fast since it will be used for generating unique IDs for billions of objects. It doesn't need to be a cryptographic hash function, nor does it ...
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### Problem with efficiency of projective coordinates in Elliptic Curve arithmetic

Ok sort of long post incoming. Will go slow to make it as clear as possible I'm trying to build a C library for Elliptic Curve Arithmetic. Since the idea is to learn from the process, I decided to ...
• 95
1 vote
92 views

### Constant-time decompression on an elliptic curve

Let $E\!: y^2 = f(x)$ be an elliptic curve over a finite field $\mathbb{F}_{q}$ of odd characteristic. Consider an $\mathbb{F}_{q}$-point $P = (x,y)$ on $E$. Suppose that we only have the $x$-...
56 views

### Merge two multisignatures

I want to know if there is a multisignature scheme that allows the merging of two multisignatures for the same data but by two different sets of users, and without knowing the corresponding private ...
191 views

### Number of rounds for constant header size in common hashes and XOFs

We compute hash $H(M_0\mathbin\|M_1)$ of size $d\ge1$ for some constant header $M_0$ of size $m_0$, and $\nu\ge1$ messages $M_1$ of random content and size $m_1$. For Merkle-Damgård hashes, a simple ...
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721 views

### Why Crypto++ library's AES definition is so fast

I am trying to compare the CPU cycle required for two encryption algorithms. One algorithm is AES and lets the other algorithm is B(code name). I implemented algorithm B and having fewer and simpler ...
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### zkSnark Circuit

In practice, the circuit need to be proved always has a large size, maybe nearly billion gates, when turns such circuit to QAP, it will generate a large polynomial, which is a high cost to use zkSNARK....
• 95
1 vote
189 views

### Lookup table for DSA/ECDSA/Schnorr multiplication

Something in common to [EC]DSA and related signature schemes like Schnorr is that the most expensive part of signing is calculating $r = g^k$ in the group for some per-signature $k$ of length $b$ bits....
• 2,585
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### Optimized Garbled Circuit Algorithmic Description

The Garbled Circuit (GC) is now over thirty years old, and many optimization methodologies have been proposed, including point-and-permute, row-reduction, free-XOR, fixed-key blockcipher, half-and. ...
• 149
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### Why Salsa20 rotates columns vertically to optimize for SIMD?

I'm writing a school assignment and I'm trying to fully grasp the differences between Salsa20 and ChaCha. I've come to understand that by rotating upwards the initial matrix columns, DJB says that ...
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### Prove you computed $hash^r(input)$ for some cryptographic hash function

What is the most efficient way to prove that a person computed $r$ rounds of some cryptographic hash function (ex. SHA256) on an input? Specifically, I'm trying to optimize (1) the running time of the ...
290 views

### Hardware optimized stream ciphers?

As I understand it, ChaCha20 is slower than AES-CTR in hardware. Are there any hardware-optimized stream ciphers?
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1 vote