← Entropy Atlas
Secret & unpredictable
Ephemeral handshake secrets
Short-lived secret values help two parties establish a fresh session key.
Evaluation card
What “plenty” means here.
- Required property
- An unpredictable value generated for the scheme, normally anew for each handshake.
- If it fails
- Reuse or prediction can expose sessions and may erase forward-secrecy benefits.
- Relevant attacker
- A network observer who records handshakes and may later compromise long-term keys.
- The Plenty Line
- Match the group’s security strength and generate through the operating system’s CSPRNG for each required exchange.
- Why more is not automatically better
- The group and protocol cap security; longer improvised secret material does not repair a weak group.
Where it appears
Recognize the pattern.
- 01TLS ephemeral key exchange
- 02secure-messaging ratchets
- 03VPN handshakes
The Plentropy rule
Protect the requirement, then stop.
Match the group’s security strength and generate through the operating system’s CSPRNG for each required exchange.
Once that claim has comfortable evidence and margin, improve the next limiting factor instead of worshipping a larger entropy number.