SRP-6a 2048-bit group

Purpose

srp-group.ts exports the canonical 2048-bit MODP group from RFC 5054 Appendix A as bigint constants. The SRP-6a client uses this group to exchange ephemeral keys, derive the shared secret, and produce mutual proofs. The constants are pinned because they are part of the protocol contract — switching groups silently would break interoperability with every server using the same RFC.

Features

SRP_N_2048 — the 2048-bit safe prime N as a positive bigint.
SRP_G — the generator g = 2.
SRP_N_BITLEN = 2048, SRP_N_BYTELEN = 256 — convenience constants for byte-padding and validation.

Usage: Basic Example

import { SRP_G, SRP_N_2048 } from "@suaveplan/crypto-vault/srp/srp-group";
console.log(SRP_N_2048.toString(2).length); // 2048
console.log(SRP_G); // 2n

Usage: Advanced Example

import {
    SRP_G,
    SRP_N_2048,
    SRP_N_BITLEN,
    SRP_N_BYTELEN,
} from "@suaveplan/crypto-vault/srp/srp-group";
import { pow } from "@noble/curves/abstract/modular";

// Compute v = g^x mod N for an arbitrary private key x.
function makeVerifier(x: bigint): bigint {
    return pow(SRP_G, x, SRP_N_2048);
}

console.log(SRP_N_BITLEN); // 2048
console.log(SRP_N_BYTELEN); // 256
console.log(typeof makeVerifier(123n)); // bigint

API Reference

`SRP_N_2048: bigint`

The exact 2048-bit safe prime defined in RFC 5054 Appendix A, parsed from the canonical hex constant.

`SRP_G: bigint`

The generator: 2n.

`SRP_N_BITLEN: number`, `SRP_N_BYTELEN: number`

Bit length (2048) and byte length (256) of the prime.

Implementation Notes

The hex string is laid out as a TypeScript string concatenation matching the line breaks in the RFC for diffability against the source.
The constant is parsed once at module load; subsequent imports share the resulting bigint.
The 1024-bit and 1536-bit groups from the same RFC are intentionally omitted. RFC 5054 §1 states they should be deprecated for new deployments, and the proposal pins us to ≥ 2048 bits.

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