Crypto

Because not all crypto is TLS.

Live streaming Cryptopals

Oh, wow. I love the idea. Would anyone here seriously watch 20 to 40 hours of me doing crypto, math and Go? Mic, screen, and everything. https://t.co/jx3s736bGm— Filippo Valsorda (@FiloSottile) October 16, 2016 Almost a year after promising to, I recently started live-coding in Go solutions…

The scrypt parameters

The recommended scrypt parameters in the Go docs were recently brought up for discussion given they haven't changed since 2009. Even if at this point I memorized the three numbers (N=16384, r=8, p=1) I only have a vague understanding of their meaning, so I took some time…

Playing with kernel TLS in Linux 4.13 and Go

Linux 4.13 introduces support for nothing less than... TLS! The 1600 LoC patch allows userspace to pass the kernel the encryption keys for an established connection, making encryption happen transparently inside the kernel. The only ciphersuite supported is AES-128-GCM as per RFC 5288, meaning it only supports TLS version…

restic cryptography

tl;dr: this is not an audit nor an endorsement and I take no responsibility, but I had a quick look at the crypto and I think I'm going to use restic for my personal backups. I keep hearing good things about restic. I am redoing my storage solution, and…

I'm giving up on PGP

After years of wrestling GnuPG with varying levels of enthusiasm, I came to the conclusion that it's just not worth it, and I'm giving up. At least on the concept of long term PGP keys. This is not about the gpg tool itself, or about tools at all. Many already…

TLS nonce-nse

Starting a series of blog posts on TLS 1.3, I published my notes on the landscape of cipher nonces in TLS across versions, to help me clean up the implementation. Comes with hand-drawn diagrams! TLS nonce-nse | CloudFlare Blog (archive)…

An overview of TLS 1.3

I presented TLS 1.3 to the CloudFlare London office. Why it's faster, how it works, why it's safer, what's clever about it. The talk is recorded and comes with colored diagrams. There's a transcript on the CloudFlare blog. Update: you might want to watch my 33c3 talk on the…

So I lost my OpenBSD FDE password

The other day I set up a new OpenBSD instance with a nice RAID array, encrypted with Full Disk Encryption. And promptly proceeded to forget part of the passphrase. We know things get interesting when I lose a password. I did a weak attempt at finding some public bruteforce tool,…

"LuckyMinus20": Yet Another Padding Oracle in OpenSSL CBC Cipher Suites

Early this week, a new OpenSSL error code padding oracle dropped. Padding oracles are one of the most fun crypto vulnerabilities, so I gave this one the full treatment: a ten lines PoC and CLI test, obviously based on a patched Go crypto/tls https://github.com/FiloSottile/CVE-2016-2107 an…

Bleichenbacher'06 signature forgery in python-rsa

While looking at the source of python-rsa (>100K daily downloads) I found it vulnerable to a straightforward variant of the Bleichenbacher'06 attack against RSA signature verification with low public exponent. The bug allows us to forge signatures for arbitrary messages, as long as the public key has a low exponent…

Logjam explained

Logjam is a downgrade attack against the TLS protocol itself which exploits EXPORT ciphersuites. I wrote a long explanation of how the attack works and its background (what Diffie-Hellman is and how exactly it's used in the TLS handshake) on the CloudFlare blog. Logjam: the latest TLS vulnerability explained | CloudFlare…

scrypt all the things!

If you take away only one thing from this post let it be this: If you have a human password, scrypt it. The reason passwords suck is because humans are terrible at generating and storing entropy. (That and password reuse, but that's another story.) And the reason that's a problem…

Salt & Pepper, please: a note on password storage

Everyone will tell you that the best practice for password storage is [sb]crypt with random salt. Ok, we got that and even maybe got everyone to agree. But let me bump that up a notch: do you know what pepper is? The concept of peppering is simple: add a…

On Keybase.io and encrypted private key uploading

One thing in particular of Keybase.io attracts a lot heat recently: they support uploading your encrypted key on their servers. This usually is pointed at as a mortal sin. Well, here is my private key, the untouched output of gpg --armor --export-secret-keys filippo.io | gpg --armor --clearsign. -----BEGIN PGP…

The ECB Penguin

This is an image that has become kind of a cultural icon in the cryptography and InfoSec community. I'm speaking about "the penguin", a picture of the Tux Linux mascot encrypted with a block cipher in ECB mode that still shows clearly the outline of the original. [email protected] @ErrataRob ECB…