side channel attack based on the different speed at which certain operations are executed.

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Attacking Scrypt Under Access Pattern Leakage

Could cache-timing channels (such as exist for certain block ciphers) somehow be made use of in order to extract memory-access pattern information if both the attacker and user are NOT in a shared ...
9
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1answer
108 views

Is it possible to test implementation for side-channel attacks?

When it comes to implementing cryptographic algorithms, there seems to be a big focus on the difficulty of doing so without introducing the potential for side channel attacks and the knowledge ...
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29 views

correlation between the timing data produced by different keys with similar inputs in AES

Is there or can there be any correlation between the timing data produced by different keys with similar inputs in AES? If yes, what type of correlation?
5
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1answer
236 views

Do key-dependent S-boxes make efficient constant-time software implementations almost impossible?

It seems to me that algorithms like Blowfish and Twofish with key-dependent S-boxes are almost impossible to implement without table lookups, and thus are almost impossible to implement in software ...
9
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2answers
81 views

Do I need to worry about timing attacks in Base64 encoding/decoding of private keys?

Do I need to worry about timing attacks in Base64 encoding/decoding of private keys? This is a common operation (ex. PEM keys) and is variable time in typical implementations.
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1answer
26 views

Single-scalar multiplication with sign bit

I want to know if there's an "easy" timing-free way to compute the sign of $y$-coordinate of $r G$, for a secret scalar $r$ and $G$ the generator of an elliptic curve. We have several choices for ...
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21 views

Is ISAAC vulnerable to a cache timing attack?

Is the ISAAC stream cipher vulnerable to a cache timing attack in efficient implementations? It seems like it would (secret-dependent array lookups) but is it exploitable in the context of ISAAC?
3
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0answers
31 views

is accessing elements of an array in secret order vulnerable to timing attack?

Suppose there is an array containing bytes 0...255. Suppose this array is shuffled using a key for random data. Since this is indexing the elements of a table using secret data, is it vulnerable to ...
3
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0answers
32 views

how exploitable are cache timing attacks

So there's a PHP package that's been recently written to protect against cache timing attacks: https://www.reddit.com/r/PHP/comments/4a1iuh/rfc_4648_character_encoding_written_to_resist/ My question ...
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1answer
35 views

Is it okay to use a variable-time RSA implementation to verify TLS certificates?

RSA as implemented by OpenSSL et al. needs to protect against side channel attacks, at a big performance penalty. However, TLS certificate validation involves no secrets. Therefore, I should be able ...
2
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1answer
35 views

Are timing attacks exploitable if each key is used only once?

Suppose that one performs (for example) AES-GCM encryption and decryption using an algorithm that is vulnerable to timing attacks, but each key is used only once. Is it still possible to perform a ...
4
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1answer
89 views

ChaCha20 immune to timing attacks

What are the reasons because of which ChaCha20 is immune to timing attacks ? Also why is not AES immune to timing attacks?
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30 views

Is it okay to bail out early when length mismatch is detected?

Is it okay to bail out early when length mismatch is detected? Specifically, when verifying authenticated encryption, is it okay to bail out early if the wrong amount of ciphertext or the wrong ...
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0answers
56 views

Importance of timing attack resistance with AES

I've implemented AES in my library with several variations: a straight C version, a version using x86 SSSE3, and a version using x86 AES-NI. The SSSE3 and AES-NI implementations are constant-time, ...
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2answers
45 views

Are there any disadvantages of using libsodiums helpers for en-/decoding/comparision instead of the native ones?

Libsodium has some helpers, which allow hexdecimal decoding, encoding and also constant-time string comparison. So if you use the php binding libsodium-php you ...
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1answer
33 views

Would buffering socket send resist timing attacks

I have been reading and thinking about timing attacks on cryptographic systems. The answer to this question mentions the following: "The way to defend against timing attacks is to make sure the time ...
3
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1answer
208 views

RSA: Most significant key bit always 1?

Is it possible to say that the most significant bit of an RSA private exponent is always 1? Wouldn't that weaken the key strength by exactly that one bit? I refer to the paper "Timing Attack: What ...
8
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1answer
160 views

Branchless AES Implementation

Imagine a branchless implementation of the AES-128 cipher. Are there any benefits over the implementation that contains branches, other than possible prevention of timing attacks? Is it even true, ...
5
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2answers
237 views

Should Increment functions be near-constant time?

When operating a block cipher in CTR or GCM mode, should the function used to increment the counter or initialization vector be near-constant time? Here, I'm wondering about the "addition with carry" ...
3
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1answer
151 views

Double randomised HMAC verification to prevent timing attack

A way to prevent timing attacks for hash string comparison is to perform additional HMAC signing in order to randomize the verification process (see Double HMAC Verification). In addition to the ...
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30 views

Is a timing side channel attack effective when the leaked information is related to the result of a hash?

I'm writing a function to act as a cryptographic hash of a number within a range that returns another number of the same range. The catch is that the result needs to have certain properties. I run a ...
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1answer
65 views

What are coding schemes for timing channels

I know we can hide information in the inter-packet delays, e.g. we can generate a code-book that each code-word corresponds to a message and is generated by realization of a specific random process. ...
10
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1answer
1k views

Why do crypto libs use table lookups when they're vulnerable to timing attacks?

AESEngine.java, from BouncyCastle, uses table lookups as does aes_x86core.c, in OpenSSL. But per Cache-timing attacks on AES table lookups like what OpenSSL and BouncyCastle are doing are vulnerable ...
3
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1answer
65 views

Can string lookups be vulnerable to timing attacks like array lookups are?

Per “Can non-assembly crypto libraries truly be secure against timing attacks?”, array lookups are vulnerable to timing attacks. Like, if you do cresult[map[i]] and ...
7
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1answer
340 views

Can non-assembly crypto libraries truly be secure against timing attacks?

http://cr.yp.to/antiforgery/cachetiming-20050414.pdf states the following: So what went wrong? Answer: NIST failed to recognize that table lookups do not take constant time. “Table lookup: not ...
3
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3answers
855 views

Practical Uses for Timing Attacks on Hash Comparisons (e.g. MD5)?

Consider the following code snippet: ...
3
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1answer
146 views

Double-and-add/Montgomery VS blinding

I'm having a hard time understanding why people use constant-time techniques to counter time-attacks, when blinding seems as good and cheaper to implement. Why do people avoid blinding in ECC?
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53 views

Cache Attacks on Cloud Infrastructures

I read something about cache attacks like this: Enter KSM (Kernel SamePage Merging). KSM enables the kernel to examine two or more already running programs and compare their memory. If any memory ...
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1answer
85 views

Do asymmetric signatures require constant-time verification?

To avoid a timing attack, HMAC signatures are usually compared in constant-time (every byte is compared, and the results aggregated). Is the same necessary for asymmetric signature algorithms such ...
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1answer
186 views

Defence against timing attacks

I know this is a difficult subject but would a good defense against timing attacks be not sending a message if the decryption or authentication fails? So if the attacker provides a wrong HMAC for ...
3
votes
1answer
123 views

Performing HMAC with random key before MAC comparison

In Laravel (a PHP framework) I can see that they calculate a HMAC with a random key over the final HMAC before comparison. This additional HMAC calculation is of course performed for both the ...
0
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1answer
60 views

TimeStamp in Cache-time attacks on AES [closed]

I have recently read about AES cache timing attacks. More specifically, I read Daniel Bernstein paper Cache-timing attacks on AES. I have a question about the code in Appendix A: ...
2
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0answers
121 views

Timing Attack on OpenSSL by Brumley

I am referring to this paper by David Brumley and Dan Boneh: Remote Timing Attacks are Practical (In proceedings of the 12th Usenix Security Symposium, 2003). In this paper on page 4, Brumley ...
2
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0answers
115 views

RSA Key Blinding

I was looking the answer to the following question (Timing attack on modular exponentiation), discussing the Private Key Blinding as a countermeasure for timing attacks. Therefore I'm asking if ...
2
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1answer
200 views

“Fine grain Cross-VM Attacks on Xen and VMware are possible” and OpenSSL 0.9.7

Here's a paper that just made its way into Cryptology ePrint Archive: Fine grain Cross-VM Attacks on Xen and VMware are possible!. Its a good survey of past attacks and presents a couple of new ...
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126 views

RSA timing attack

Given an RSA implementation that uses Montgomery multiplications and CIOS exp algo, but NOT CRT. Given a decryption1 oracle that takes chosen cipher text and responds the plain text and the time it ...
2
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0answers
108 views

Timing attacks against RSA, DH and AES

I have been reading about “Timing Attacks on RSA: Revealing Your Secrets through the Fourth Dimension” by Wing H. Wong. I was wondering if this attack is feasible while signing with RSA and, if yes, ...
1
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1answer
171 views

Attacking hashed password by timing attack and other means

This question is inspired by this recent one, which raises a point that need to be made quantitative to be meaningfully discussed. I chose an unusual approach: a new question worded as homework that ...
7
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1answer
493 views

Timing attack on RSA as used by CryptoLocker?

So far I have researched timing attacks on RSA, We all know the ransomware named CryptoLocker uses RSA 2048 bit encryption. Now, is it possible to break the encryption using a timing attack. I have ...
5
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3answers
837 views

Timing Attacks on ECDSA, ECDHE, AES and SHA2

Are there any known timing attacks (both practical and theoretical) on any implementations of the following? ECDSA (I'm aware of this one - are there any applicable to prime fields?), ECDHE (again, ...
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0answers
313 views

Does BouncyCastle (for ECC) resist timing attacks?

I need to extend the TLS protocol to be able to use other key exchange scheme based on elliptic curves. I am planning to use BouncyCastle's implementation in Java and in .NET. I am worring about ...
3
votes
1answer
135 views

Potential vulnerability in DH key selection - am I understanding this right?

I'm reading through a DH implementation, and I think I found a potential hole. Public $p$ and $g$ values are properly selected. A candidate secret value $\bar a$ is pseudo-randomly selected such ...
10
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3answers
792 views

Stopping timing attacks on AES: Why is it important to prevent the OS from interrupting the AES computation?

I read the paper Cache-timing attacks on AES (by Daniel J. Bernstein), but I don't seem to understand everything. The author dedicates a long section on how to prevent the OS to interrupt an AES ...
5
votes
1answer
1k views

AES timing attacks

I'm just interested in cryptography, so please don't expect me to be an expert. ;) I recently read about AES cache timing attacks and found it very interesting. I read the article Cache-timing attacks ...
3
votes
1answer
239 views

Attack vectors introduced by compilers

I have a question about attacks on the implementation of cryptographic code that are enabled by compilation and compiler-optimisations. I am aware of this. Would anyone be able to point me to other ...
7
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1answer
223 views

Are more complex algorithms easier to break with timing attacks?

Is there a point where increasing the complexity of an encryption algorithm will make it easier to break using a timing attack? Or is there no connection here at all?
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3answers
3k views

Known methods for constant time (table-free) AES implementation using 'standard' operations?

There are several known methods for implementing AES in constant time using SIMD operations, mostly based around fast byte shuffling (for instance Hamburg and Kasper/Schwabe). Are there any similar ...