Questions tagged [side-channel-attack]

attacks using information leaked by implementations of cryptographic algorithms to obtain information about keys or (plaintext) data, instead of (or additional to) using cryptographic weaknesses.

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109 views

How to express difficulty of breaking crypto when writing?

When writing for both technical and non-technical readers I find my self naturally wanting to write things such as : "..therefore it would be impossible to decrypt the data." When trying ...
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Does Argon2id provide less protection against side-channel attacks than Argon2i theoretically and/or practically? [duplicate]

LUKS 2 encryption uses Argon2i as the default PBKDF. As the key is used on each access, I guess side-channel attacks are a significant threat factor. However, as I'm not a cryptographer, I am not ...
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3answers
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How practical are side-channel attacks and how much of a concern are they?

I see a lot of research in very sophisticated side-channel attacks on crypto systems. Most (but definitely not all) seem to follow a trend, namely, the crypto system does something very dumb like ...
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52 views

Are side-channels possible in KDFs

Are KDFs such as PKDF2 and HKDF vulnerable to side-channel attacks such as static and dynamic power analysis including the hash type used internally?
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54 views

Stream slicing operation in block cipher and side-channel attack

My symmetric block cipher works kind of like a stream cipher, but it works on $128$-bit blocks. It generates a $128$-bit block in every round. And at the end of the round, I have to slice it into two ...
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1answer
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Constant Time algorithms for $\mathbb{Z}/m\mathbb{Z}$, $\mathbb{Z}/m\mathbb{Z}[x]$, and $\mathbb{Z}/m\mathbb{Z}[x] / (f(x))$?

I want to implement some (lattice based) protocols to better familiarize myself with a programming language (Rust). These tend to do arithmetic over rings like $\mathbb{Z}/m\mathbb{Z}$, or "...
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1answer
511 views

Cracking a key using a combination of partial keys

As part of a cryptanalytic attack I've carried out, I used a divide-and-conquer strategy to divide the secret key $k$ into several equal-sized partial keys $k = {k_1, k_2, ...}$. The attack works ...
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1answer
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What is the Lord of the Ring(s): Side Channel Attack and What are the results

A recent Paper to appear on USENIX Security 2021 titled as Lord of the Ring(s): Side Channel Attacks on the CPU On-Chip Ring Interconnect Are Practical by Riccardo Paccagnella Licheng Luo Christopher ...
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1answer
58 views

Is this constant-time comparison secure?

I was thinking about constant-time comparison and how it differs from "==", when I thought of a simple way that's could be constant-time. Being a beginner in cryptography, I'd like to know ...
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Conditional probability being Constant in Threshold Cryptography

I am working on Threshold implementation of algorithms to prevent side channel attacks. I am not that much proficient in Statistics and Probability theory. I want to know what is the significance of ...
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secp256k1 scalar decomposing and prime field arithmetic

I'm currently studying the elliptic curve secp256k1 implementation. In my understanding, it has efficiently computable endomorphisms: We can find out a pair of number $\lambda$ and $\beta$ from the ...
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Is this “AND” implementation safe against side channel attacks?

I found out that the following is a working implementation of calculating an AND function between XOR masked shares, implementation at Github. It works by calculating parities, whose terms cancel each ...
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2answers
815 views

Side-Channel Attacks in the Cloud

Let's say we have some very sensitive personal files. At all costs, we do not want any other pair of eyeballs to gaze upon them. We need these sensitive files to be secure and available. So, we have ...
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Dragonfly masked DH

I was looking at Dragonfly key exchange protocol RFC 7664, and it seems to make use of masked Diffie-Hellman in the final part. Generating two random numbers less than group order $q$, $m$, and $r$ ...
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1answer
751 views

Does blinding work against side channel on RSA?

In the so called "blinding" technique for RSA, prior to decryption, the ciphertext is multiplied by random $r$ raised to the power of $e$; e.g., $C$ is replaced with $C\cdot r^e$; and then after ...
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340 views

Why does side-channel security focus on “shielding” rather than “jamming”?

I have always found it weird when in a crypto discussion people stressed the importance of making algorithms runtime-deterministic, to the point of avoiding any compiler optimisations. To me, it seems ...
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1answer
241 views

How can I avoid side channel attacks to scalar multiplication of Ed25519?

I'm a beginner at working with Edwards Curves, and I'm trying to implement an Ed25519 signature. I have a question from a text. Please see the illustration below (in Python). At the part of scalar ...
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2answers
815 views

What is a “constant time” work around when dealing with the point at infinity for prime curves?

I've been working for some time, on designing a constant time solution for dealing with the "point at infinity" for prime curves. So, far I'm using the Standard Projective Coordinates for ...
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Constant time arithmetic implementation in DSA

I am trying to understand why it is a hard problem to have formally verified constant time arithmetic for DSA when compared with ECDSA. For instance, in ECDSA implementations of OpenSSL, we have ...
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Hashing of variable-length chunked data leading to leakage of secret key from side channel?

Hypothetically, secret data could be hashed in some schemes in one way or another. Could chunking of the data lead to exposure of secret component through side channel? Say converting a randomized ...
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1answer
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Why shouldn't cryptocurrency hash algorythms, resist side channel attack?

2015's Argon2 publication suggests that cryptocurrency hashing like password hashing on backend servers should not be subject to side-channel attack: Argon2d is optimized for settings where the ...
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2answers
85 views

Side channel attack - execution time depends on the size of the key

In my algorith execution time depends on the size of the key. It is a linear relationship (probably). The larger the key, the longer the algorithm takes to run. I have a code in Python so far. For ...
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Is “double-and-add-always” a good mitigation against side channel attacks?

In Discrete Log based Cryptography, one of the core operations that one, has to perform is modulo exponentiation. There are many algorithms to choose from, especially, when considering my point of ...
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Will OTP provide quantum resistance under 5 conditions?

We already have quantum computing, but when quantum computing becomes commercially available there is a problem for many but not all encryption algorithm. The One-Time-Pad or OTP is the one and only ...
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1answer
165 views

Have crypto side-channel attacks happened in the wild?

I'm aware of attacks extracting information via timing and volume. But none that care or attack the actual cryptographic algorithm implementation or end up extracting the key. Seeking examples if any ...
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RSA least significant bit oracle attack

I have been reading up on RSA attacks and came across one that could be called a least-significant-bit (LSB) oracle attack. For the sake of clarity lets define RSA primes $(p, q)$, private key $d$ ...
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How to find the output shares of first-order threshold implementation of cubic degree function?

Assume $d=abc$ and to implement first order threshold implementation , the minimum input and output shares are 4 (1*3+1) , and 4 , calculated using ${4\choose 3}$ , Theorem 2. The new TI ...
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1answer
55 views

Shuffling: Purpose and formal definition

To my understanding, shuffling means simply to permute the elements in vector $\mathbf{v}$ pseudorandomly, using a PRP $\pi (\mathrm{seed},\mathbf{v})$. A secure PRP should yield a permutation ...
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495 views

Constant time multiplication in GF(2^8)

I am trying to implement AES in C; I would like to make it resistant to side-channel attacks but I can't implement the multiplication in constant time. My current code: ...
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1answer
84 views

What quality of randomness is needed for randomized side channel countermeasures?

Using per-operation randomness is a popular and effective way to protect cryptographic implementations against side-channel attacks, e.g. using Shuffling (randomizing the processing order eg for AES ...
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How to implement arbitrary s-box in a side-channel-free way in C?

This could be a question for CodeReview.SE, but I thought it might require non-trivial cryptographic knowledge to merit it on-topic here. The C language is chosen as it's a common language for ...
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How vulnerable are SIMD operations to side channel attacks?

For a while, I was experimenting with optimization of several crypto implementations with SIMD (Single Instruction Multiple Data ) made available by C compiler ...
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1answer
2k views

Safely sorting secret data

Suppose you have a secret list of n distinct integers. How would you sort this list in a way that is not vulnerable to timing attacks? I tried looking up "...
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1answer
155 views

Is AES without T-Tables nor S-Box resistant to side-channel?

T-Tables and S-Boxes are prone to side-channel attacks, is an implementation without any lookup tables resistant to side-channel ? In this answer, https://crypto.stackexchange.com/a/63520/80926, the ...
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1answer
146 views

Is AES S-Box resistant to side-channel attacks?

I know that implemntations with T-tables such as Golang's are prone to side-channel attacks, but is AES's S-Box wihtout any additional table also insecure ?
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1answer
155 views

Timing attacks on homomorphic encryption

I've been wondering for a long time about programs that could potentially break fully homomorphic encryption schemes: ...
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1answer
534 views

Deterministic RSA blinding

I have an implementation of the RSA private key operation in a context where I don't have access to an entropy source. I'd like to add blinding to it (both message and exponent), to make it resist ...
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1answer
60 views

Application of Non-deterministic Processors in side channel attacks

I was reading the abstract of "Non-deterministic Processors" paper by "David MayHenk L. MullerNigel P. Smart", in the abstract, they have mentioned the Kocher paper about "Timing Attacks on ...
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2answers
5k views

How are side-channel attacks executed? What does an attacker need to execute a side channel attack?

I've been reading about side-channel attacks on Wikipedia, and it seems that some of these can only be executed on the victim's computer. (I am specifically asking about the side-channel attacks ...
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488 views

Conditions for a successful Differential Power Analysis attack

From this paper, there are two conditions for a successful DPA attack: i) there exists an intermediate variable in the implementation that is correlated with the power consumption and ii) this ...
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2answers
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Can deterministic ECDSA be protected against fault attacks?

In a paper by Barenghi and Pelosi, it was described that fault attacks could be used to derive the secret key when using deterministic ECDSA as described in RFC6979 by @Thomas_Pornin Deterministic (...
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How to prevent cache timing attack on table lookup AES implementation?

I've been trying to find a solid method to prevent cache timing or other possible side channel attacks on an AES implementation, that uses lookup tables for S-box substitution. I realize that there ...
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How does breaking AES with a side channel attack (CPA) differ from a side channel attack on something like a microcontroller?

I'm studying CPA side channel attacks. CPA stands for Correlation Power analysis and it can be used to break AES. I'm familiar with the process to crack AES on a microcontroller. I was just wondering ...
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1answer
133 views

Does clustering the AES Sbox look up table to 32 bit entry per index, help reduce vulnerability to cache timing attacks?

I've been searching for some, easy methods to help mitigate, a cache timing attack on software AES implementations. Currently, my implementation uses, a usual 256 byte S-box ...
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1answer
2k views

How to confirm my implementation is constant time

I'm implementing Schnorr signatures following a variant used in Bitcoin Cash (BCH) of this algorithm: GitHub - Schnorr Signatures for secp256k1. A notable difference is that the BCH schnorr algorithm ...
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1answer
110 views

Is it possible to perform CPA(Correlation Power Analysis) when attacker has only specific round's waveform?

I read Quite a lot document about breaking AES using CPA. But most of them, assuming that attacker has the first or last round of the waveform(trace) and exploit SubBytes. My question is if the AES-...
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How does a cache timing attack work on AES with lookup tables?

I was trying to make a software only implementation of AES (Rijndael). At first I was able to implement it using table lookups for the Galois field multiplication and also for the SBox, but, I really ...
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Should I delete cryptographic data from memory?

When dealing with cryptographic data, is there a chance that attacker recovers portion of data I used in my program? Should I try to delete every bit of keys and encrypted data that I used, overwrite ...
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1answer
104 views

How many AES-operations have to be watched for key-exploit by side-channel attacks?

If I would like to exploit a used key by side-channel attack, one that measures electromagnetic fields, how many runs of the AES-128 do I need to spy on for a successful exploit? I can't use any ...
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3k views

How to avoid side channel attacks when handling large numbers?

For cryptography, the platforms have limited size as 32 or 64-bit operations. We definitely need big numbers to implement the encryption/decryption and digital signatures for cryptosystems like RSA, ...