Frederik Deweerdt
Distinguished Engineer at Fastly
San Francisco, California, United States
Summary
🤩
RockstarFrederik Deweerdt is a Distinguished Engineer with 26 years of systems and security-focused software engineering experience, based in San Francisco. He currently drives low-level network and crypto work at Fastly, combining deep protocol knowledge with pragmatic engineering to harden production systems. An active open-source contributor, Frederik has improved TLS 1.3 and QUIC implementations—fixing security-critical bugs, adding fuzzers, and addressing concurrency and buffer-overflow risks in h2o/picotls and h2o/quicly. He excels at surfacing subtle reliability and randomness issues in cryptographic code and turning them into robust, testable fixes. Colleagues rely on him for thoughtful code-level reviews and practical mitigations that bridge research-grade cryptography and real-world deployment.
26 years of coding experience
French, Spanish, English
Stackoverflow
5,101reputation
683kreached
64answers
2questions
networking
top-1%
browser
top-5%
virtual-machine
top-1%
linux-kernel
top-5%
linux
top-5%
gcc
top-5%
Github Skills (27)
it-security10
virtual-machine10
c1110
tls1310
networking10
security10
c1710
asn110
quic10
cryptography10
fuzzing10
gcc9
linux-kernel9
linux9
browser9
Programming languages (10)
Github contributions (5)
h2o/picotls
Mar 2017 - May 2022
TLS 1.3 implementation in C (master supports RFC8446 as well as draft-26, -27, -28)
Role in this project:
Back-end Developer & Security Engineer
Back-end Developer & Security EngineerContributions:8 reviews, 48 commits, 15 PRs in 5 years 2 months
Contributions summary:Frederik contributed to the `picotls` repository by fixing bugs related to security vulnerabilities and code optimizations. They implemented fixes to improve the randomness in cryptographic operations and addressed potential buffer overflows. The user also added fuzzers for ASN1 validation and type/length checks and introduced features for raw certificate handling, enhancing the security and robustness of the TLS 1.3 implementation.
cryptographysslocsptlsmaster
h2o/quicly
Oct 2017 - Jun 2021
A modular QUIC stack designed primarily for H2O
Role in this project:Back-end Developer
Back-end DeveloperContributions:4 reviews, 14 commits, 19 PRs in 3 years 9 months
Contributions summary:Frederik's contributions primarily involved enhancements and bug fixes to the `quicly` codebase, a QUIC stack. They added a packet fuzzer for testing, expanded the codebase to handle command-line arguments, and addressed a concurrency issue. The user also resolved an issue in the context of a crypto library call and made improvements to the overall codebase by cleaning up the context of connection close.
quich2ohttp3protocolh3
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