V8 JIT Optimizations Break Constant-Time Guarantees in JS Crypto Library

jedisct1 · x · 2026-09-12

Security blogger Soatok discloses that PhD student Yayu Wang found a side-channel in constant-time-js: V8's JIT compilation can compile key-dependent code and undermine algorithmic constant-time design. The author had long warned compiler/runtime optimizations can defeat such guarantees, kept the library demo-only, and has shipped a 0.5.0 fix.

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