✳flâneur — a map of the web's best reading

Why are the lower 3 bits of curve25519/ed25519 secret keys cleared during creation? - Cryptography Stack Exchange

crypto.stackexchange.com · 1,756 words · saved by 1 readers

Stack Exchange network consists of 183 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers. Now available on Stack Overflow for Teams! AI features where you work: search, IDE, and chat. Ask questions, find answers and collaborate at work with Stack Overflow for Teams. Explore Teams Teams Q&A for work Connect and share knowledge within a single location that is structured and easy to search. I am currently experimenting with ed25519 and I noticed that on secret key creation, bit 254 is always set and the lower 3 bits are always cleared. I found that bit 254 is always set to protect against timing attacks in this question: When using Curve25519, why does the private key always have a fixed bit at 2^254? But why are the lower 3 bits cleared. Obviously it has to do with the formula in the curve25519 paper: The set of secret keys is defined to be { 𝑛 ⎯ ⎯ :𝑛∈ 2

Why are the lower 3 bits of curve25519/ed25519 secret keys cleared during creation? - Cryptography Stack Exchange The 2026 Annual Developer Survey is live— take the Survey today! . Stack Internal Knowledge at work Bring the best of human thought and AI automation together at your work. Explore Stack Internal Why are the lower 3 bits of curve25519/ed25519 secret keys cleared during creation? Ask Question Asked 12 years, 7 months ago Modified 12 years, 7 months ago Viewed 6k times 27 $\begingroup$ I am currently experimenting with ed25519 and I noticed that on secret key creation, bit 254

Explore this link on the map →

related reading