salsa20 vs chacha20

To learn more, see our tips on writing great answers. If you want to use Salsa instead, then just replace ChaCha20 with Salsa20 - but I would rather not do that. […] This post is about why I dislike AES-GCM’s design, not “why AES-GCM is insecure and should be avoided”.

XSalsa20 feeds the key and the first 128 bits of the nonce into one block of Salsa20 (without the final addition, which may either be omitted, or subtracted after a standard Salsa20 block), and uses 256 bits of the output as the key for standard Salsa20 using the last 64 bits of the nonce and the stream position. Making statements based on opinion; back them up with references or personal experience.

ChaCha20 provides more diffusion than Salsa20.

It's highly recommended to use a MAC like Poly1305 with ChaCha/Salsa because data encrypted with stream ciphers are subject to malicious bit flip attacks. Can we finally know the difference between these words? (It calso also be argued that GCM is simply a combination of CTR with GMAC). Never use ECB mode.

Unlike AES-GCM, AES-CTR doesn’t provide any message integrity guarantees.

In addition, the ChaCha quarter-round diffuses changes more quickly. Although I previously stated that AES-GCM is possibly my least favorite AEAD, AES-CCM is decidedly worse: AES-GCM is Encrypt-then-MAC, while AES-CCM is MAC-then-encrypt.

Finding the smallest function and the domain on which it is smallest. Specifically, the 256 bits of output used are those corresponding to the non-secret portions of the input: indexes 0, 5, 10, 15, 6, 7, 8 and 9.

(in bytes). It's always recommended to use 20 rounds XChaCha/XSalsa with Poly1305.

However, if your threat model includes “AES is broken or backdoored by the NSA”, a cipher cascade using AES is safer than just selecting a nonstandard cipher instead of AES. How do you set, clear, and toggle a single bit? If you do not, AES-GCM is either slower than ChaCha20-Poly1305, or it leaks your encryption keys in cache timing. Question- now that I have it working with the one block of 1024 bytes, assuming that I now want to read/write from a much larger file.... can I use the same nonce to re-initialize the IV each time (right before each call to ECRYPT_encrypt_bytes()), or must I change the nonce for each read/write? Wasn't ChaCha20 proven to be no less secure than the Salsa20 core? ChaCha was published while eSTREAM was still running. Why does the manual for inner tube say max psi is 4.5? Salsa20/12 is now in the final eSTREAM portfolio. Here's my best attempt so far, starting with one small string of plaintext (my C is rusty... it's possible I've made some basic mistake, though I can't see it): Encrypting [THIS IS A TEST] using random 256 bit key and 64 bit IV: Probably (as DJ BERNSTEIN claimed himself), ChaCha is a variant of salsa20 As he wrote many papers with many versions on this subject, he need time to stabilize them. The algorithms are significantly different: AES-GCM is a simpler algorithm to analyze. If you have to choose between the two, go for ChaCha. To the authors of these configuration files, I have but one question: Sure, you might think, “But Blowfish supports up to 448-bit keys and is therefore more secure than even 256-bit AES.”. If I found two $5 bills on the ground, would it be acceptable to say "$10 are on the ground"? Use MathJax to format equations.

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Tension between "publishable" and "motivating" research topics. Performance.

I agree that conservatism is the likely reason for the choice in McBits. It uses a new round function that increases diffusion and increases performance on some architectures.

grep - print the file name for the file grep currently is searching in, Computer simulation of squeezing flexible objects with force. By using our site, you acknowledge that you have read and understand our Cookie Policy, Privacy Policy, and our Terms of Service.

Two consecutive rounds (column-round and row-round) together are called a double-round: An implementation in C/C++ appears below. [17] The Aumasson et al. https://www.google.com/url?sa=t&source=web&rct=j&url=https://cr.yp.to/snuffle/xsalsa-20081128.pdf&ved=2ahUKEwiB2ff7o8foAhVRzDgGHW9BCG0QFjADegQIAxAB&usg=AOvVaw3pfOfep6cl9gtvXr-xP9I4, Wikipedia page for more information about the original Chacha20 and Salsa20 : What is this oddly shaped hinged device with indentations? https://tools.ietf.org/html/draft-irtf-cfrg-xchacha-03, See Google's blog post on using Chacha20 Poly1305: As stated in the comments, dev/random already produces cryptographically secure random bytes which are perfectly adequate for use in encryption keys.

Use the key and the first 128 bits of the nonce (in input words 12 through 15) to form a ChaCha input block, then perform the block operation (omitting the final addition). (MAC then Encrypt). The two stream ciphers were submitted to the eSTREAM competition, and they have stood the test of time as of now. Better security comes from AES-GCM-SIV, better encryption performance comes from AES-GCM.

Is it appropriate for peer-reviewer to look for possible plagiarism? They are even using it in their disk encryption project Adiantum

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encKey := HmacSha256(“encryption-cbc-hmac”, key), macKey := HmacSha256(“authentication-cbc-hmac”, key), ciphertext := AesCbc(plaintext, iv, encKey), tag := HmacSha256(iv + ciphertext, macKey), encKey := HmacSha256(“encryption-ctr-hmac”, key), macKey := HmacSha256(“authentication-ctr-hmac”, key), ciphertext := AesCtr(plaintext, nonce, encKey), tag := HmacSha256(nonce + ciphertext, macKey).

Making statements based on opinion; back them up with references or personal experience. (This same technique is widely used in hash functions from MD4 through SHA-2.). It's like riding a bike I guess :) Unfortunately, I've found complex samples online (like the eSTREAM test suite) and samples in other languages... but no direct simple implementation in C (probably because I'm just missing some basic concept here which is supposed to be self-evident). Thanks! If I recall correctly Chacha20 was only analyzed by two papers prior to getting into TLS. To subscribe to this RSS feed, copy and paste this URL into your RSS reader.

Yes, it can be implemented as an AEAD cipher, although the common definition uses ChaCha20 instead. announced a cryptanalysis of Salsa20 which breaks 8 out of 20 rounds to recover the 256-bit secret key in 2255 operations, using 211.37 keystream pairs. Crypto++ 5.6.0 Benchmarks. Asking for help, clarification, or responding to other answers. Running these bytes through another CSPRNG is completely redundant.

best. This double-speed update is the most important difference between ChaCha and Salsa20.

This attack makes use of the new concept of probabilistic neutral key bits for probabilistic detection of a truncated differential. The Signal Protocol uses AES-CBC + HMAC-SHA2 for message encryption. Block cipher modes that support initialization vectors were invented to compensate for this shortcoming.

Yes, the IV is safe to transmit as plaintext.

Reduced-round variants are thus appreciably faster. MathJax reference. AES-CBC requires a padding scheme (e.g. For applications where this is not enough, such as file or disk encryption, RFC 7539 proposes using the original algorithm with 64-bit nonce. If you must use AES-CBC, then you must also MAC your ciphertext (and the initialization vector–IV for short). What kind of writing would be considered offensive?

The whole point of "pure" AEAD algorithms like GCM is to avoid all the pitfalls in manually combining a encryption algorithm with a MAC. Change ), Software, Security, Cryptography, and Furries, on Comparison of Symmetric Encryption Methods, A Word on Anti-Furry Sentiments in the Tech Community, Kerlissions – Trivial Collisions in Iota’s Hash Function (Kerl), Designing New Cryptography for Non-Standard Threat Models – Dhole Moments, that AES-GCM is possibly my least favorite AEAD, AES-GCM-SIV is also vulnerable to the Invisible Salamanders attack, second HMAC call with a random per-comparison key, a robust extended-nonce key-splitting scheme. Pretty much every mainstream application of Salsa20 is in fact a Salsa/Poly1305 construction. Use MathJax to format equations.

[1] However, reduced round variants Salsa20/8 and Salsa20/12 using 8 and 12 rounds respectively have also been introduced.

All were coded in C++, compiled with Microsoft Visual C++ 2005 SP1 (whole program optimization, optimize for speed), and ran on an Intel Core 2 1.83 GHz processor under Windows Vista in 32-bit mode.

( Log Out /  Key size isn’t everything. I guess it has inherited some trust from Salsa20, but what other merits does it have? ChaCha, Salsa, including their eXtended nonce versions are all stream ciphers and Poly1305 is the authentication mechanism that provides integrity to the data encrypted along with the unencrypted associated data.

In response to this, a variant called ChaCha was … AEAD stands for Authenticated Encryption with Associated Data.

Therefore you can use any secure underlying cipher with Poly1305 ! ChaCha is a modification of Salsa20 published in 2008.

Conclusion: Both are good options. Stack Exchange network consists of 176 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. There seems to be a lot of interest among software developers in the various cryptographic building blocks (block ciphers, hash functions, etc. Simplicity and Cost are huge too but more like guiding principles. How do you use bcrypt for hashing passwords in PHP? [3], In 2012, the attack by Aumasson et al. What is nscf calculation in Quantum ESPRESSO? The Salsa quarter-round function. AES-GCM is an authenticated encryption mode.

The reduced-round ciphers Salsa20/12 and Salsa20/8 are among the fastest 256-bit stream ciphers available and are … 128 bits ChaCha6 within 2 , but claims that the attack fails to break 128 bits ChaCha7. [14] However, this attack does not seem to be competitive with the brute force attack. AES is a block cipher with a 128-bit block size. By using our site, you acknowledge that you have read and understand our Cookie Policy, Privacy Policy, and our Terms of Service. Which tasks can be visually confirmed by other crew members?

Change ), You are commenting using your Google account. When we calculate mean and variance, do we assume data are normally distributed?

The core function maps a 256-bit key, a 64-bit nonce, and a 64-bit counter to a 512-bit block of the key stream (a Salsa version with a 128-bit key also exists).

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy. It's because both Salsa and ChaCha are resistant to side channel attacks and very easy to implement in software.

x86/MMX/SSE2 assembly language routines were used for integer … What are you doing?

The library will pad for you, but you can do it too.

[25], ChaCha20 is also used for the arc4random random number generator in FreeBSD[26], OpenBSD[27], and NetBSD[28] operating systems, instead of the broken RC4, and in DragonFly BSD[29] for the CSPRNG subroutine of the kernel. Creating a new user breaking existing permissions.

Ask me about dholes or Diffie-Hellman! Assume that we have a large file which can be read in chunks of 1024 bytes or so, how can I encrypt and decrypt each chunk using Salsa or Chacha 20?

The encrypt/decrypt functions increment the offset, giving your code a different IV for the encryption and decryption functions. paper also attacks ChaCha, achieving one round fewer: for 256 bits ChaCha6 with complexity 2 and ChaCha7 with complexity 2 . [7][8] XSalsa20 is provably secure if Salsa20 is secure, but is more suitable for applications where longer nonces are desired. Why is the Economist model so sure Trump is going to lose compared to other models?

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