Cranim: A Toolkit for Cryptographic Visualization
Let’s kick this off with some examples. Here’s a seamless loop illustrating CBC-mode encryption: Here’s a clip showing a code block being rewritten to avoid leaking padding information in error messages: Here’s an illustration of a block cipher operating in CTS mode: You may be surprised to learn that each of these illustrations was generated […]
Announcing the Cryptopals Guided Tour Video 17: Padding Oracles!
Hello and welcome back to the Cryptopals Guided Tour (previously, previously)! Today we are taking on Challenge 17, the famous padding oracle attack. For those who don’t know, Cryptopals is a series of eight sets of challenges covering common cryptographic constructs and common attacks on them. You can read more about Cryptopals at https://cryptopals.com/. There’s a […]
Exploiting Noisy Oracles with Bayesian Inference
In cryptographic attacks, we often rely on abstracted information sources which we call “oracles”. Classic examples include the RSA parity oracle attack, which depends on an oracle disclosing the least-significant bit of a ciphertext’s decryption; Bleichenbacher’s attack on PKCS#1v1.5 RSA padding, which depends on an oracle for whether a given ciphertext’s decryption is correctly padded; […]
Announcing NCC Group’s Cryptopals Guided Tour: Set 2
Hello and welcome to NCC Group’s Cryptopals guided tour! This post is the second in a series of eight installments (previously) covering the solutions to the Cryptopals Crypto Challenges. For those who don’t know, Cryptopals is a series of eight sets of challenges covering common cryptographic constructs and common attacks on them. You can read […]
Announcing NCC Group’s Cryptopals Guided Tour!
Hello and welcome to NCC Group’s Cryptopals guided tour! This post is the first in a series of eight installments covering the solutions to the Cryptopals Crypto Challenges. These have been a long time coming, and we’re excited to finally start bringing them to you. For those who don’t know, Cryptopals is a series of […]
Cryptopals: Exploiting CBC Padding Oracles
This is a write-up of the classic padding oracle attack on CBC-mode block ciphers. If you’ve done the Cryptopals cryptography challenges, you’ll remember it as challenge 17. This is a famous and elegant attack. With it, we will see how even a small data leak (in this case, the presence of a “padding oracle” – […]