# `keys/oid`

## Purpose

Centralised OID constants for the RSA wire formats handled by this package.
Currently exports `OID_RSA_ENCRYPTION` (`1.2.840.113549.1.1.1`), the algorithm
identifier RFC 8017 uses for `rsaEncryption` inside `SubjectPublicKeyInfo`
and `PrivateKeyInfo` `AlgorithmIdentifier` slots. Future stages may extend
this file with the signature-OID family (`sha256WithRSAEncryption` etc.) once
the sign/verify modules need them; this Stage-1 file covers the universal
key-format OID alone.

## Features

- One definition per OID — eliminates copy-paste drift between parsers.
- String-typed OIDs (`"1.2.840.113549.1.1.1"`) match the dotted-decimal form
  produced by `DerReader.readObjectIdentifier`.

## Usage: Basic Example

```ts
import { OID_RSA_ENCRYPTION } from "@suaveplan/crypto-rsa";

if (oid === OID_RSA_ENCRYPTION) {
    // dispatch to RSA path
}
```

## Usage: Advanced Example

```ts
import { OID_RSA_ENCRYPTION } from "@suaveplan/crypto-rsa";
import { encodeNull, encodeObjectIdentifier, encodeSequence } from "@suaveplan/crypto-rsa/asn1";

const algorithmIdentifier = encodeSequence(
    encodeObjectIdentifier(OID_RSA_ENCRYPTION),
    encodeNull()
);
```

## API Reference

### `OID_RSA_ENCRYPTION: "1.2.840.113549.1.1.1"`

The PKCS #1 `rsaEncryption` algorithm identifier per RFC 3279 §2.3.1, RFC 5280
Appendix A, and RFC 8017 Appendix A.1.

## Implementation Notes

The constant is exposed as a string rather than a typed brand because
`DerReader.readObjectIdentifier` returns plain strings, and direct equality
checks remain trivially constant-time at the byte level. A branded type would
add complexity without security benefit at this layer.