golang.org/x/crypto v0.54.0: blake2b.New256

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify blake2b.New256 in pkg:golang/golang.org/x/crypto@v0.54.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/crypto@v0.54.0
Demonstrate these symbols/APIs:
  - blake2b.New256
Constraints:
  - executionContext: node
Required runtime conditions:
  - ecosystem: npm
  - language: javascript
  - moduleSystem: cjs
  - packageManager: npm@10.9.8
  - runtime: node@22.23.2

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

package sample

import (
	"bytes"
	"testing"

	"golang.org/x/crypto/blake2b"
)

func TestNew256BasicProperties(t *testing.T) {
	h, err := blake2b.New256(nil)
	if err != nil {
		t.Fatalf("expected nil error, got %v", err)
	}
	if size := h.Size(); size != 32 {
		t.Fatalf("expected size 32, got %d", size)
	}
	if blockSize := h.BlockSize(); blockSize != 128 {
		t.Fatalf("expected block size 128, got %d", blockSize)
	}
}

func TestNew256MatchesSum256(t *testing.T) {
	data := []byte("The quick brown fox jumps over the lazy dog")
	h, err := blake2b.New256(nil)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}
	h.Write(data)
	digest := h.Sum(nil)

	expected := blake2b.Sum256(data)
	if !bytes.Equal(digest, expected[:]) {
		t.Fatalf("digest mismatch: got %x, expected %x", digest, expected)
	}
}

func TestNew256WithKey(t *testing.T) {
	data := []byte("authenticated message")
	key := []byte("secret-key-up-to-64-bytes-long")

	hKeyed, err := blake2b.New256(key)
	if err != nil {
		t.Fatalf("unexpected error with valid key: %v", err)
	}
	hKeyed.Write(data)
	keyedDigest := hKeyed.Sum(nil)

	hUnkeyed, err := blake2b.New256(nil)
	if err != nil {
		t.Fatalf("unexpected error with nil key: %v", err)
	}
	hUnkeyed.Write(data)
	unkeyedDigest := hUnkeyed.Sum(nil)

	if bytes.Equal(keyedDigest, unkeyedDigest) {
		t.Fatalf("expected keyed digest to differ from unkeyed digest")
	}
	if len(keyedDigest) != 32 {
		t.Fatalf("expected 32-byte digest, got %d bytes", len(keyedDigest))
	}
}

func TestNew256KeyTooLong(t *testing.T) {
	key65 := make([]byte, 65)
	_, err := blake2b.New256(key65)
	if err == nil {
		t.Fatalf("expected error for key longer than 64 bytes, got nil")
	}
}

func TestNew256Reset(t *testing.T) {
	data := []byte("test data for reset")
	h, err := blake2b.New256(nil)
	if err != nil {
		t.Fatalf("unexpected error: %v", err)
	}

	h.Write(data)
	digest1 := h.Sum(nil)

	h.Reset()
	h.Write(data)
	digest2 := h.Sum(nil)

	if !bytes.Equal(digest1, digest2) {
		t.Fatalf("expected identical digests after Reset, got %x vs %x", digest1, digest2)
	}
}

{"case":{"caseId":"case:sha256:a397f90ff5bb331ed9a936dd83605d4a5306ba1043cf1a26ac9a8ef30aa7b0e1","contract":["blake2b.New256(nil) returns a 32-byte hash.Hash with BlockSize 128 without error","blake2b.New256(nil) digest matches blake2b.Sum256 output for identical inputs","blake2b.New256 with a non-nil key up to 64 bytes functions as a MAC producing keyed digests","blake2b.New256 returns an error when key length exceeds 64 bytes","blake2b.New256 hasher Reset clears state allowing subsequent digest recomputation"],"goal":"verify blake2b.New256 in pkg:golang/golang.org/x/crypto@v0.54.0","kind":"HOW","packages":["pkg:golang/golang.org/x/crypto@v0.54.0"],"schemaVersion":1,"symbols":["blake2b.New256"]},"contractCommand":["go","test","./..."],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","language":"go","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","packageManagerVersion":"1.26.6","runtime":"go","runtimeVersion":"1.26","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/golang.org/x/crypto@v0.54.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/crypto@v0.54.0","symbols":["blake2b.New256"],"verifierAdapter":"golang@1"}

module sample-98948192

go 1.26.6

require golang.org/x/crypto v0.54.0

require golang.org/x/sys v0.47.0 // indirect

golang.org/x/crypto v0.54.0 h1:YLIA59K4fiNzHzjnZt2tUJQjQtUWfWbeHBqKtk3eScw=
golang.org/x/crypto v0.54.0/go.mod h1:KWL8ny2AZdGR2cWmzeHrp2azQPGogOv+HeQaVEXC2dk=
golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=

package sample

import (
	"hash"

	"golang.org/x/crypto/blake2b"
)

// Hash256 computes the BLAKE2b-256 digest of data with an optional MAC key.
func Hash256(data []byte, key []byte) ([]byte, error) {
	h, err := blake2b.New256(key)
	if err != nil {
		return nil, err
	}
	h.Write(data)
	return h.Sum(nil), nil
}

// NewHasher returns a new BLAKE2b-256 hash.Hash instance.
func NewHasher(key []byte) (hash.Hash, error) {
	return blake2b.New256(key)
}

{
  "schemaVersion": 1,
  "goal": "verify blake2b.New256 in pkg:golang/golang.org/x/crypto@v0.54.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/crypto@v0.54.0"
  ],
  "symbols": [
    "blake2b.New256"
  ],
  "constraints": {
    "executionContext": "node"
  },
  "runtimeConditions": {
    "ecosystem": "npm",
    "language": "javascript",
    "moduleSystem": "cjs",
    "packageManager": "npm@10.9.8",
    "runtime": "node@22.23.2"
  }
}