# `keys/serialize-pkcs8`

## Purpose

Inverse of `parseRsaPrivateKeyPkcs8`. Wraps a serialised PKCS#1
`RSAPrivateKey` in a DER `PrivateKeyInfo` per RFC 5208 §5, emitting the
canonical `version 0` form (RFC 5958 `version 1` requires the optional
`publicKey [1]` field which Stage 1 does not emit).

## Features

- Standard PKCS#8 emission with `version 0`.
- Reuses `serializeRsaPrivateKeyPkcs1` so the inner OCTET STRING body
  matches the PKCS#1 output bit-for-bit.
- RFC 3279 §2.3.1 conformant `NULL` algorithm parameters.

## Usage: Basic Example

```ts
import { serializeRsaPrivateKeyPkcs8 } from "@suaveplan/crypto-rsa";

const pkcs8 = serializeRsaPrivateKeyPkcs8(key);
```

## Usage: Advanced Example

```ts
import {
    parseRsaPrivateKeyPkcs8,
    serializeRsaPrivateKeyPkcs8,
} from "@suaveplan/crypto-rsa";

const roundTripped = parseRsaPrivateKeyPkcs8(
    serializeRsaPrivateKeyPkcs8(key)
);
```

## API Reference

### `serializeRsaPrivateKeyPkcs8(key: RsaPrivateKey): Uint8Array`

Returns the DER-encoded `PrivateKeyInfo`.

## Implementation Notes

We emit `version 0` (RFC 5208) rather than `version 1` (RFC 5958) because
Stage 1 does not have a public-key derivation pipeline yet. Stage 4 may
add a `version 1` emission path that includes the `[1] publicKey` field
for ecosystems (cosign, sigstore) that prefer the OneAsymmetricKey form.