Malleability of ECDSA (and DSA) signatures, JWTs, etc.
Published:
This blog posts explains that ECDSA and DSA signatures are malleable, that JWTs can be malleable as well and how this can be used to bypass some broken implementations of JWT deny lists (for revocation of JWTs or anti-replay protection).
If you are trying to understand the difference between the different cryptography-related formats (PKS#12, PKCS#8, PEM, X.509 certificate, DER, JWK, BEGIN ENCRYPTED PRIVATE KEY??? 🤯), you will hopefully find some useful information here (and a lot more your did not wanted to know about).
Some notes about how TLS v1.3 works. This is a follow-up of the previous episode about TLS v1.2. As before, the goal is to have a high-level overview about how the protocol works, what is the role of the different messages and be able to understand (and debug) a network traffic dump.
Some notes about how TLS v1.2 (Transport Layer Security) works. The goal explain what is going on in a network traffic dump, the role of the different TLS extensions, the impact of the different cipher suites on security, etc. It includes several diagrams and many references.
The Diffie-Hellman (DH) key exchange (and variants thereof) is widely used in many protocols (such as TLS, SSH, IKE (IPSec), Signal, etc.) to bootstrap some symmetric key material which may then be used to secure communication channel between two parties. This introduction focuses on the different ways the DH key exchange is used in practice in several protocols (especially TLS) and the impact of these different approaches on the security. This is intended as a prelude for the upcoming next episodes about how TLS works.