59 lines
8.0 KiB
Markdown
59 lines
8.0 KiB
Markdown
# `groups-2048`
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<!-- begin:auto-docs -->
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_(no submodules)_
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<!-- end:auto-docs -->
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- [groups-1024](./1024/groups-1024.md) — <!-- begin:auto-docs --> _(no submodules)_- [1536](./1536/groups-1536.md) — <!-- begin:auto-docs --> _(no submodules)_ - [groups-1536](./1536/groups-1536.md) — <!-- begin:auto-docs --> _(no submodules)_- [3072](./3072/groups-3072.md) — <!-- begin:auto-docs --> _(no submodules)_ - [groups-3072](./3072/groups-3072.md) — <!-- begin:auto-docs --> _(no submodules)_- [4096](./4096/groups-4096.md) — <!-- begin:auto-docs --> _(no submodules)_ - [groups-4096](./4096/groups-4096.md) — <!-- begin:auto-docs --> _(no submodules)_- [6144](./6144/groups-6144.md) — <!-- begin:auto-docs --> _(no submodules)_ - [groups-6144](./6144/groups-6144.md) — <!-- begin:auto-docs --> _(no submodules)_- [8192](./8192/groups-8192.md) — <!-- begin:auto-docs --> _(no submodules)_ - [groups-8192](./8192/groups-8192.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-2048](./groups-2048.md) — <!-- begin:auto-docs --> _(no submodules)_- groups-1024 — <!-- begin:auto-docs --> _(no submodul…
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- [groups-1024](./1024/groups-1024.md) — <!-- begin:auto-docs --> _(no submodules)_- [1536](./1536/groups-1536.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-1536](./1536/groups-1536.md) — <!-- begin:auto-docs --> _(no submodules)_- [3072](./3072/groups-3072.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-3072](./3072/groups-3072.md) — <!-- begin:auto-docs --> _(no submodules)_- [4096](./4096/groups-4096.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-4096](./4096/groups-4096.md) — <!-- begin:auto-docs --> _(no submodules)_- [6144](./6144/groups-6144.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-6144](./6144/groups-6144.md) — <!-- begin:auto-docs --> _(no submodules)_- [8192](./8192/groups-8192.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-8192](./8192/groups-8192.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-2048](./groups-2048.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-1024](./1024/groups-1024.md) — <!-- begin:auto-docs --> _(no submodules)_- [1536](./1536/groups-1536.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-1536](./1536/groups-1536.md) — <!-- begin:auto-docs --> _(no submodules)_- [3072](./3072/groups-3072.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-3072](./3072/groups-3072.md) — <!-- begin:auto-docs --> _(no submodules)_- [4096](./4096/groups-4096.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-4096](./4096/groups-4096.md) — <!-- begin:auto-docs --> _(no submodules)_- [6144](./6144/groups-6144.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-6144](./6144/groups-6144.md) — <!-- begin:auto-docs --> _(no submodules)_- [8192](./8192/groups-8192.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-8192](./8192/groups-8192.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-2048](./groups-2048.md) — <!-- begin:auto-docs --> _(no submodules)_- groups-1024 — <!-- begin:aut…
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- [groups-1024](./1024/groups-1024.md) — <!-- begin:auto-docs --> _(no submodules)_- [1536](./1536/groups-1536.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-1536](./1536/groups-1536.md) — <!-- begin:auto-docs --> _(no submodules)_- [3072](./3072/groups-3072.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-3072](./3072/groups-3072.md) — <!-- begin:auto-docs --> _(no submodules)_- [4096](./4096/groups-4096.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-4096](./4096/groups-4096.md) — <!-- begin:auto-docs --> _(no submodules)_- [6144](./6144/groups-6144.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-6144](./6144/groups-6144.md) — <!-- begin:auto-docs --> _(no submodules)_- [8192](./8192/groups-8192.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-8192](./8192/groups-8192.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-2048](./groups-2048.md) — <!-- begin:auto-docs --> _(no submodules)_- groups-1024 — <!-- begin:auto-docs --> _(no submodu…
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- [groups-1024](./1024/groups-1024.md) — <!-- begin:auto-docs --> _(no submodules)_- [1536](./1536/groups-1536.md) — <!-- begin:auto-docs --> _(no submodules)_ - [groups-1536](./1536/groups-1536.md) — <!-- begin:auto-docs --> _(no submodules)_- [3072](./3072/groups-3072.md) — <!-- begin:auto-docs --> _(no submodules)_ - [groups-3072](./3072/groups-3072.md) — <!-- begin:auto-docs --> _(no submodules)_- [4096](./4096/groups-4096.md) — <!-- begin:auto-docs --> _(no submodules)_ - [groups-4096](./4096/groups-4096.md) — <!-- begin:auto-docs --> _(no submodules)_- [6144](./6144/groups-6144.md) — <!-- begin:auto-docs --> _(no submodules)_ - [groups-6144](./6144/groups-6144.md) — <!-- begin:auto-docs --> _(no submodules)_- [8192](./8192/groups-8192.md) — <!-- begin:auto-docs --> _(no submodules)_ - [groups-8192](./8192/groups-8192.md) — <!-- begin:auto-docs --> _(no submodules)_- [groups-2048](./groups-2048.md) — <!-- begin:auto-docs --> _(no submodules)_
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## Purpose
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The bundled 2048-bit safe-prime group from RFC 5054 Appendix A. This is the default SRP-6a group every consumer of `@suaveplan/srp` gets without any additional import: `N_2048` is a 256-byte modulus, `g_2048` is the single byte `0x02`, and `BIT_LENGTH` is the literal `2048`. RFC 5054 deliberately bundles a small set of fixed safe primes to side-step trust-on-first-use over arbitrary moduli; we ship the 2048-bit one as the default because it sits at the contemporary security floor while keeping a 2048-bit `modPow` cheap enough (~5–20 ms) for an interactive login.
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## Features
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- `N_2048` byte-exact to RFC 5054 Appendix A "2048-bit Group" literal.
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- `g_2048` equal to `Uint8Array([2])`.
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- `BIT_LENGTH` literal-typed `2048`.
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- Frozen `Uint8Array`s — consumers cannot mutate the shared constant.
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- Reachable from the root `@suaveplan/srp` barrel AND from `@suaveplan/srp/groups`.
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## Usage: Basic Example
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```ts
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import { N_2048, g_2048, BIT_LENGTH } from "@suaveplan/srp/groups";
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console.log(N_2048.byteLength); // 256
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console.log(g_2048[0]); // 2
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console.log(BIT_LENGTH); // 2048
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```
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## Usage: Advanced Example
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```ts
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import { N_2048, g_2048 } from "@suaveplan/srp/groups";
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import { defaultHashBridge } from "@suaveplan/srp/hash";
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import { params2048Sha256 } from "@suaveplan/srp/params";
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const params = params2048Sha256(defaultHashBridge("SHA256"));
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// params.N is the same shared reference as N_2048.
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// Use this params object for client + server handshakes.
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```
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## API Reference
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| Export | Type | Description |
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| ------------ | -------------- | -------------------------------------------------------------- |
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| `N_2048` | `Uint8Array` | 256-byte modulus from RFC 5054 Appendix A. |
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| `g_2048` | `Uint8Array` | Single-byte generator `0x02`. |
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| `BIT_LENGTH` | `2048` | Literal bit length of `N_2048`. |
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## Implementation Notes
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The modulus is encoded as a hex literal in source rather than embedded as a base64 blob so a human reader can diff it against RFC 5054 Appendix A line-by-line. The hex string is split into eight 64-char chunks matching the eight rows the RFC prints. The byte-exact unit test (`groups-2048.test.ts`) reconstructs the same hex from the `Uint8Array`, uppercases it, and asserts equality against the same literal.
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`g_2048` is `Uint8Array([2])` rather than a `bigint` because every place SRP mixes group elements into a hash uses `PAD(g)` over the group modulus; expressing `g` as a one-byte buffer up-front avoids a runtime `bigint`-to-bytes conversion at every hash site. The single-byte representation also matches the byte-shape every `Uint8Array`-keyed helper in this package expects.
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The `BIT_LENGTH` literal is typed `2048` (not `number`) so consumers narrowing on the constant get a literal type back. This matters in test files where we assert that the bundled group is exactly the RFC's 2048-bit choice and not, say, a future 3072-bit upgrade.
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