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Questions tagged [side-channel]

A side channel attack is an attack that deduces secret information from environmental observations such as timing or power consumption.

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Why are performance counters not used for cache attacks?

Cache side-channel attacks rely on the capability to observe cache hits/misses for a given set. Usually this is done via timing information, e.g. in flush+reload or prime+probe. Why is the performance ...
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3 votes
1 answer
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Does this theoretical salted-hash-sleep scheme mitigate timing attacks?

This question is purely theoretical, I have no intention of ever implementing this scheme in practice. I'm familiar with the shortcomings of sleeping as means of mitigating timing attacks. I'm more ...
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Side-channel impacts of coil whine and related acoustical phenomena over time

I am aware of one paper (although I forget the name) in which an AES key is extracted from some meters away as a result of coil whine (potentially audible vibration of an inductor coil), but I can't ...
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How are code-branch side channel attacks mitigated on Java?

When you are working with secret keys, if your code branches unequally it could reveal bits of the secret keys via side channels. So for some algorithms it should branch uniformly independently of the ...
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6 answers
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Does having no 'if' blocks in code mitigate side-channel attacks?

Looking through descriptions of Spectre and Meltdown it seems that speculative execution - the basis for these attacks - occurs only with branched code. Therefore, it seems logical to conclude that ...
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Use side-channel attack to steal file with permission 600? [closed]

Alice and Bob are on the same file system. Alice made a spam filter plugin, which reads /tmp/mail and then writes the report to /tmp/report. The /tmp/mail has permission 400 and /tmp/report has ...
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Is using a developer key to protect a REST API good practice?

I'd like to implement a RESTful API service over HTTP that developers can call from their server side environments. I intend to use a cryptographically secure pseudo-random number generator (CSPRNG) ...
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Constant-Time String-to-Byte Encoding for JavaScript

When dealing with cryptographic secrets (private keys, passwords, etc) it is desirable to not run these secrets through functions that do not run in constant time, in order to avoid the potential for ...
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1 answer
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Are CPU side-channel attacks still a concern on VPSs

I've been looking into getting a VPS to run an OpenVPN server on and a few other things. I've been speaking to a hosting company and they have sent me this screenshot to show they are protected ...
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Is protecting against Meltdown and Spectre on virtual servers actually possible?

I've been reading into the Meltdown and Spectre bugs recently and the issues they cause for virtualised servers, as memory in one VM can potentially be accessed by another user in a separate VM with ...
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7 votes
1 answer
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How sensitive are acoustic side-channels to compression with a narrowband codec?

Assume sensitive audio emissions from a mechanical keyboard. These audio emissions are often sufficient to reconstruct the actual key presses that generated the sound. If the audio is compressed using ...
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Timeless timing attacks and response jitter

I've been researching timeless timing attacks, ie: timing attacks using concurrency rather than round trip time. Here is an article by portswigger with links to the original article by Van Goethem. ...
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In the time side channel, is there any way to improve the measurement time accuracy?

I want to measure the execution time of a function. The execution time of this function is only slightly different in the two cases. Is there any way I can accurately measure its time to distinguish ...
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Compiler-induced information leaks/side-channels in cryptography implementations

In Cryptography Engineering Ferguson, Schneier and Kohno put a big emphasis on quality of code in order to prevent it from leaking information and from being vulnerable to memory corruption exploits. ...
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Academic/Campus WiFi Security - Setup: Open

At CERN the WiFi used, is not using any encryption. This means that it is a plain, standard Wi-Fi network with no authentication. However, it is mandatory to register each device when first connecting ...
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FLUSH + RELOAD Proof of Concept - Why do we need to flush more than needed?

Problem I am putting together a proof of concept for the FLUSH + RELOAD attack. The method is outlined in great detail in this paper. The general idea is simple - cached addresses can be accessed with ...
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Prefetch Side-Channel Attacks:Bypassing SMAP and Kernel ASLR

I'm trying to understand and perform the Prefetch Side-Channel Attacks:Bypassing SMAP and Kernel ASLR. The author have released the proof-of-concept code. I'm trying to run the attack on my Intel ...
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Use delay with a fixed total time to defend against timing attacks

Consider this common example used to demonstrate timing attacks: async def sign_in(username, password): user = await get_user_from_db(username) if user is None: return False # early return :(...
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1 vote
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Does TLS 1.3 mitigate the BREACH vulnerability?

Section 5.4 of the TLS 1.3 specification describes record padding. One of the mitigations for BREACH is to add random padding. Therefore, I'm wondering: Does TLS 1.3 require random record padding? I'...
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security of AES where attacker can ask secure code to decrypt arbitrary cypher-text

A service or library provides a function decrypt( user_id, cypher_text) and gives back plain text. Internally to the function it loads an AES key from a secure vault, decrypts the cypher_text, and ...
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3 votes
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Can string comparison realistically be exploited in a timing attack on a web server?

Suppose you have the following code in Node: const { token } = req.body const hash = crypto.createHmac('sha256', SECRET).update(token).digest('hex') const user = await User.findById(req.session....
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How are websites actually mititating BREACH? (HTTPS + compression)

After reading some popular questions and answer on this website about BREACH, the only advice seems to be: don't compress anything that might contain secrets (including CSRF tokens). However, that ...
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Meltdown/Spectre attack

What concepts should a newbie(someone who doesn't have too much knowledge about computer architecture, user/kernel space, memory etc.) understand if he wants to know how Metldown/Spectre works? I ...
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19 votes
5 answers
4k views

How can I prevent side-channel attacks against authentication?

After reading this excellent answer, I learned about the existence of side-channel attacks. From the code example provided, it is possible to determine the correct password by timing the code when ...
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What kind of attacks can hardware level memory encryption protect from?

Both AMD and Intel have introduced memory encryption at the hardware level. AMD calls this Secure Memory Encryption (SME), with the Intel version being Total Memory Encryption (TME). What kind of ...
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Cache side-channels: Prime & Probe attack

I am having trouble to completely understand the Prime & Probe attack: My current understanding is this: Priming phase: The attacker occupies all cache sets with attacker data. Probe phase: The ...
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1 vote
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How would one compare Cache Allocating Technology against MIT's Dynamically Allocated Way Guard for prevention of the Spectre side-channel Attack?

Upon research, I'm finding it difficult to identify a way to compare each solution. Is it correct in saying both solutions are software based? Therefore, could I compare overall PC perfomance with ...
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What are the new MDS attacks, and how can they be mitigated?

Several new hardware side-channels were discovered called MDS attacks, which allow reading arbitrary memory, like Meltdown. Many existing mitigations are useless against them. The relevant CVEs are: ...
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How to defeat confirmation-of-a-file attack? [duplicate]

Suppose you want to upload some files to an online storage without the storage provider figuring out what you have uploaded. The obvious thing to do is of course to encrypt the files. However, we ...
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12 votes
5 answers
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Are variable time comparisons always a security risk in cryptography code?

I came across the cryptography python package, and noticed it had the following about reporting security vulnerabilities: Examples of things we wouldn’t consider security issues: Using a variable ...
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2 answers
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Is is possible to get the TLS implemetation information of the remote server?

I am trying to devise a way to find side-channels that reveal exact TLS library (and its version) running on the remote server by adopting similar approach to JavaScript Template Attacks However, if ...
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What CPUs does the Spoiler attack affect?

I see on different websites different information about the Spoiler Attack. Some websites say all Intel CPUs are vulnerable and other websites say only Intel Core CPUs are vulnerable. Are Intel Xeon ...
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2 votes
2 answers
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Could always-listening mobile apps secretly spy on conversations?

Various apps and services available on modern smartphones constantly listen with the mic (e.g. Siri or Google Assistant listening for wake word, "Now Playing" feature on Pixel phones). To settle user ...
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badBIOS reflashing

This is not a has-badBIOS-pwn3d-me post, so don't worry about any paranoid rants. Having read a thorough analysis/debunking of the alleged evilware, I certainly understand that the technology badBIOS ...
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5 votes
1 answer
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To what extent are countermeasures against side-channel attacks effective/ used regularly by everyone?

I'm doing an Extended Essay for IB right now and I'm doing it on how secure RSA is. As side-channel attacks are one category of attack, I was wondering (as I am struggling with the conclusion) while ...
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Do any speculative executation attacks affect ARMv7 CPUs?

Do we know if there are speculative execution attacks that affect ARMv7 CPUs at this time? Are there any theoretical risks that need further investigation?
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5 votes
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Can speculative execution on intel cpu be disabled?

In the light of all the recent Intel Vulnerabilities with speculative execution, can speculative execution be fully disabled to protect from all this vulnerabilities, from BIOS or OS kernel? Maybe ...
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2 votes
3 answers
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Is malware on an air gapped computer a requirement to communicate over side-channels?

Is it a requirement to infect the air-gapped pc with malware at first to get all needed functions for a communication path between air gapped pc and attacker pc? For example: Stuxnet, first was the ...
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4 votes
1 answer
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If rowhammer only results in capacitor discharge, how can it flip 0 to 1?

In rowhammer, why will changing the voltage on one row cause the other row to open/close? Is it related to induction? How can it change bits from 0 to 1? I understand from 1 to 0 - voltage discharge, ...
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How does cache partitioning prevent covert/side-channel attacks? [closed]

In a report on an open-source separation kernel (Muen kernel) I was reading, in the future work section, it says that cache coloring can be implemented to prevent covert/side-channel attacks. It is ...
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Is the Linux kernel vulnerable to LazyFP (CVE-2018-3665)?

Recently, a side-channel attack was discovered that exploits lazy FPU state switching to leak the contents of MMX, SSE, and AVX registers. The vulnerability can only be exploited when lazy FPU saves ...
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1 vote
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Does Speculative Store Bypass Attack Require Assembly/Source Code Knowledge?

ok, so the gist of speculative store bypass attack to my understanding is that, cpu chooses the most frequent code path, bypass the if/else test and just assumes that it's true/false and then execute ...
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1 answer
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Does OpenSSH use padding of random lengths?

According to the end of RFC 4253 § 6, the random padding introduced to each SSH packet is an arbitrary multiple of 8. It mentions that random padding lengths can mitigate traffic analysis: Note that ...
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4 votes
2 answers
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Change the function such that there are no more side-channels

Given is the function compareKey which is a part of a crackme (a binary file). Which side-channel attack can be used to find the right password (password is made up by ASCII coded big and small ...
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Can cache attacks be executed on a single thread architecture?

Despite an extensive research on the subject, I'm wondering if there exists side channel attacks based on cache use which are conducted on single threaded architecture, smart cards for instance. I'm ...
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Side channel attack with flush+reload

I have been reading about cache side channel attacks and the "Flush+Reload" method came up a decent amount. Before putting forth my question, this is what I understand about the Flush+reload technique....
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2 votes
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Are there techniques or methods to develop security protocols without side channel attacks?

In general timing attacks are a manifestation of the implementation. So if I am processing data on the server or the client then I can leak information depending on how the code is written. To ...
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11 votes
1 answer
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Why does this cache attack work?

I was recently reading the following paper about doing a cache attack in Javascript: https://arxiv.org/pdf/1502.07373v2.pdf But I was confused by how it could work. In the paper, an 8 MB buffer was ...
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1 vote
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how do CPU cache side-channel attack fit into the background of Meltdown vulnerability? [duplicate]

NOTE:I know there are similar questions out there, namely this one, but that answer is just an extraction from original paper, which didn't clarify the attack. Additionally I can see from answers ...
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3 votes
2 answers
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How does the side channel actually access the contents of kernel memory in Meltdown?

In the Meltdown paper it mentions it can identify kernel memory address being accessed. The part I don't understand is how the FLUSH+RELOAD channel works to identify what the contents of the memory ...
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