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1.0.9 • Public • Published


bsrp is typescript implementation of the secure remote password (SRP) protocol, version 6a. SRP is a type of password-authenticated key exchange (PAKE) that has a couple of excellent features for authentication. It is used by 1Password, iCloud, AWS Cognito and more for login authentication.

Why SRP?

The kind lads over at 1Password provided the following rationale for using SRP:

  • authenticate without ever sending a password over the network.
  • authenticate without the risk of anyone learning any of your secrets – even if they intercept your communication.
  • authenticate both the identity of the client and the server to guarantee that a client isn’t communicating with an impostor server.
  • authenticate with more than just a binary “yes” or “no”. You actually end up with an encryption key.

B First SRP Flow

This implementation of the SRP-6a protocol requires just two API calls: image

What is different about B-first?

A B-first implementation of the SRP protocol reveals the public value B to the client before receiving the client's public value A and message. This flow is optimized for cloud-native APIs. The sister python library, also named bsrp is available for backend use here.


generateAPair(): Returns public/private ephemeral A pair

export interface APair {
  ephemeralA: BigInteger;
  publicA: BigInteger;

processChallenge(identity, password, salt, ephemeralA, publicA, publicB): Returns message and private strong session key if calculations pass SRP-6a safety checks, else null

export interface ProcessedChallenge {
  message: BigInteger;
  sessionKey: BigInteger;

verifySession(): Verifies the session and returns the evidence key if authentication is successful, else null

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  • abehoffman