# digest

## Purpose

Single canonical entry point for SHA-256 digest computation inside the SLSA
package. Deliberately routes through `@suaveplan/crypto-hash` instead of
`node:crypto` so the primitive selector layer chooses the correct backend
(Noble / WebCrypto / native) at build time, and so the package stays
runtime-agnostic for non-Node environments.

## Features

- Accepts `Uint8Array` or UTF-8 strings.
- Returns lowercase hex via `@suaveplan/crypto-utils`'s `toHex`.
- Uses the package-wide `sha256` selector — no direct noble/webcrypto import.

## Usage: Basic Example

```ts
import { computeDigest } from "@suaveplan/slsa";

const d = computeDigest("hello");
```

## Usage: Advanced Example

```ts
import { computeDigest } from "@suaveplan/slsa";
import fs from "node:fs/promises";

const artifact = await fs.readFile("./dist/@suaveplan-utils-1.2.3.tgz");
const digest = computeDigest(new Uint8Array(artifact));
// feed into generateProvenance({ artifactDigest: digest, ... })
```

## API Reference

- `computeDigest(content: Uint8Array | string): string` — returns a 64-char
  lowercase hex SHA-256. Strings are encoded as UTF-8 before hashing.

## Implementation Notes

The string branch uses `TextEncoder` (available in all modern Node / Bun /
browsers) rather than `Buffer.from(str)` so the helper remains universal.
SHA-512 is intentionally not exposed here — callers that need it should
compose `sha512` from `@suaveplan/crypto-hash` with `toHex` directly, which
keeps the SLSA surface tight and the digest format homogeneous.

### Hash Family

`digestProvenance` computes the SHA-256 of the canonical-JSON encoding of an in-toto statement and returns it as a hex string. SHA-256 is the only algorithm currently surfaced because it is the only one the Sigstore transparency log (Rekor) accepts for hashedrekord v0.0.2 entries. The helper composes `canonicalJson` and `sha256` from `@suaveplan/crypto-hash` so there is no custom hashing logic local to this module.

## Further Usage: Basic Example

```ts
import { digestProvenance } from "@suaveplan/slsa/provenance/digest";
const hex = await digestProvenance({ _type: "https://in-toto.io/Statement/v1" } as any);
```