golang.org/x/crypto v0.55.0: sha3.New256, sha3.NewShake256, sha3.Sum256

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 sha3 hash functions and SHAKE extendable-output in pkg:golang/golang.org/x/crypto@v0.55.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/crypto@v0.55.0
Demonstrate these symbols/APIs:
  - sha3.New256
  - sha3.NewShake256
  - sha3.Sum256
  - sha3.Sum512

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.

{"case":{"caseId":"case:sha256:51c94c72169788ad96c49eff78c248f7342425efea58f22392ef2d9e7a12ac90","contract":["sha3.Sum256 computes 32-byte SHA3-256 hash matching NIST FIPS 202 test vectors","sha3.Sum512 computes 64-byte SHA3-512 hash matching NIST FIPS 202 test vectors","sha3.New256 streaming hash produces identical digest to sha3.Sum256","sha3.NewShake256 derives variable-length output matching SHAKE256 test vector","sha3.NewShake256 produces deterministic output for identical input and distinct output for different input","sha3.NewShake256 Clone produces identical output stream from cloned state","sha3.NewShake256 Reset restarts stream from initial state"],"goal":"verify sha3 hash functions and SHAKE extendable-output in pkg:golang/golang.org/x/crypto@v0.55.0","kind":"HOW","packages":["pkg:golang/golang.org/x/crypto@v0.55.0"],"schemaVersion":1,"symbols":["sha3.New256","sha3.NewShake256","sha3.Sum256","sha3.Sum512"]},"contractCommand":["go","run","./test"],"environment":{"arch":"x64","distro":"ubuntu","ecosystem":"golang","libc":"glibc","libcVersion":"2.39","os":"linux","osVersionBucket":"24","packageManager":"go","schemaVersion":1},"license":"MIT-0","packages":["pkg:golang/golang.org/x/crypto@v0.55.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/crypto@v0.55.0","symbols":["sha3.New256","sha3.NewShake256","sha3.Sum256","sha3.Sum512"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.26.6

require golang.org/x/crypto v0.55.0

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

golang.org/x/crypto v0.55.0 h1:+KWHjbgOaAQ66dh/YlkZKHlz9ZUlq61AFirAR9ntP8M=
golang.org/x/crypto v0.55.0/go.mod h1:uq0V9dE/fzQuJtbnL+2EhWOE63vo164FY8xqEnV9xis=
golang.org/x/sys v0.47.0 h1:o7XGOvZQCADBQQ4Y7VNq2dRWQR7JmOUW8Kxx4ZsNgWs=
golang.org/x/sys v0.47.0/go.mod h1:4GL1E5IUh+htKOUEOaiffhrAeqysfVGipDYzABqnCmw=

package main

import (
	"encoding/hex"
	"fmt"
	"io"

	"golang.org/x/crypto/sha3"
)

func main() {
	data := []byte("Hello, CodeSampleX!")

	// 1. Fixed-output cryptographic hash functions (SHA3-256 and SHA3-512)
	hash256 := sha3.Sum256(data)
	fmt.Printf("SHA3-256: %x\n", hash256)

	hash512 := sha3.Sum512(data)
	fmt.Printf("SHA3-512: %x\n", hash512)

	// 2. Streaming hash using sha3.New256
	hasher := sha3.New256()
	hasher.Write([]byte("Hello, "))
	hasher.Write([]byte("CodeSampleX!"))
	streamingHash := hasher.Sum(nil)
	fmt.Printf("Streaming SHA3-256: %x\n", streamingHash)

	// 3. Extendable-output function (XOF) using sha3.NewShake256
	shake := sha3.NewShake256()
	shake.Write(data)

	// Derive an arbitrary-length output (e.g. 48 bytes)
	derivedOutput := make([]byte, 48)
	if _, err := io.ReadFull(shake, derivedOutput); err != nil {
		panic(err)
	}
	fmt.Printf("SHAKE-256 (48 bytes): %s\n", hex.EncodeToString(derivedOutput))
}

{
  "schemaVersion": 1,
  "goal": "verify sha3 hash functions and SHAKE extendable-output in pkg:golang/golang.org/x/crypto@v0.55.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/crypto@v0.55.0"
  ],
  "symbols": [
    "sha3.New256",
    "sha3.NewShake256",
    "sha3.Sum256",
    "sha3.Sum512"
  ]
}

package main

import (
	"bytes"
	"encoding/hex"
	"fmt"
	"io"
	"os"

	"golang.org/x/crypto/sha3"
)

func main() {
	// 1. sha3.Sum256 computes 32-byte SHA3-256 hash matching NIST FIPS 202 test vectors
	expectedEmpty256, _ := hex.DecodeString("a7ffc6f8bf1ed76651c14756a061d662f580ff4de43b49fa82d80a4b80f8434a")
	sumEmpty256 := sha3.Sum256([]byte(""))
	if !bytes.Equal(sumEmpty256[:], expectedEmpty256) {
		fmt.Fprintf(os.Stderr, "sha3.Sum256 empty input mismatch: got %x, want %x\n", sumEmpty256, expectedEmpty256)
		os.Exit(1)
	}

	expectedAbc256, _ := hex.DecodeString("3a985da74fe225b2045c172d6bd390bd855f086e3e9d525b46bfe24511431532")
	sumAbc256 := sha3.Sum256([]byte("abc"))
	if !bytes.Equal(sumAbc256[:], expectedAbc256) {
		fmt.Fprintf(os.Stderr, "sha3.Sum256 'abc' mismatch: got %x, want %x\n", sumAbc256, expectedAbc256)
		os.Exit(1)
	}

	// 2. sha3.Sum512 computes 64-byte SHA3-512 hash matching NIST FIPS 202 test vectors
	expectedEmpty512, _ := hex.DecodeString("a69f73cca23a9ac5c8b567dc185a756e97c982164fe25859e0d1dcc1475c80a615b2123af1f5f94c11e3e9402c3ac558f500199d95b6d3e301758586281dcd26")
	sumEmpty512 := sha3.Sum512([]byte(""))
	if !bytes.Equal(sumEmpty512[:], expectedEmpty512) {
		fmt.Fprintf(os.Stderr, "sha3.Sum512 empty input mismatch: got %x, want %x\n", sumEmpty512, expectedEmpty512)
		os.Exit(1)
	}

	expectedAbc512, _ := hex.DecodeString("b751850b1a57168a5693cd924b6b096e08f621827444f70d884f5d0240d2712e10e116e9192af3c91a7ec57647e3934057340b4cf408d5a56592f8274eec53f0")
	sumAbc512 := sha3.Sum512([]byte("abc"))
	if !bytes.Equal(sumAbc512[:], expectedAbc512) {
		fmt.Fprintf(os.Stderr, "sha3.Sum512 'abc' mismatch: got %x, want %x\n", sumAbc512, expectedAbc512)
		os.Exit(1)
	}

	// 3. sha3.New256 streaming hash produces identical digest to sha3.Sum256
	hasher := sha3.New256()
	if hasher.Size() != 32 {
		fmt.Fprintf(os.Stderr, "sha3.New256 Size() mismatch: got %d, want 32\n", hasher.Size())
		os.Exit(1)
	}
	if hasher.BlockSize() != 136 {
		fmt.Fprintf(os.Stderr, "sha3.New256 BlockSize() mismatch: got %d, want 136\n", hasher.BlockSize())
		os.Exit(1)
	}
	hasher.Write([]byte("quick brown "))
	hasher.Write([]byte("fox"))
	streamingDigest := hasher.Sum(nil)
	expectedDigest := sha3.Sum256([]byte("quick brown fox"))
	if !bytes.Equal(streamingDigest, expectedDigest[:]) {
		fmt.Fprintf(os.Stderr, "sha3.New256 streaming digest mismatch: got %x, want %x\n", streamingDigest, expectedDigest)
		os.Exit(1)
	}

	// 4. sha3.NewShake256 derives variable-length output matching SHAKE256 test vector
	expectedShakeAbc, _ := hex.DecodeString("483366601360a8771c6863080cc4114d8db44530f8f1e1ee4f94ea37e78b5739d5a15bef186a5386c75744c0527e1faa9f8726e462a12a4feb06bd8801e751e4")
	shake := sha3.NewShake256()
	shake.Write([]byte("abc"))
	shakeBuf := make([]byte, 64)
	if _, err := io.ReadFull(shake, shakeBuf); err != nil {
		fmt.Fprintf(os.Stderr, "sha3.NewShake256 Read failed: %v\n", err)
		os.Exit(1)
	}
	if !bytes.Equal(shakeBuf, expectedShakeAbc) {
		fmt.Fprintf(os.Stderr, "sha3.NewShake256 'abc' 64-byte mismatch: got %x, want %x\n", shakeBuf, expectedShakeAbc)
		os.Exit(1)
	}

	// 5. sha3.NewShake256 produces deterministic output for identical input and distinct output for different input
	shake1 := sha3.NewShake256()
	shake1.Write([]byte("test secret seed"))
	out1 := make([]byte, 64)
	io.ReadFull(shake1, out1)

	shake2 := sha3.NewShake256()
	shake2.Write([]byte("test secret seed"))
	out2 := make([]byte, 64)
	io.ReadFull(shake2, out2)

	if !bytes.Equal(out1, out2) {
		fmt.Fprintf(os.Stderr, "sha3.NewShake256 deterministic check failed\n")
		os.Exit(1)
	}

	shakeDiff := sha3.NewShake256()
	shakeDiff.Write([]byte("different secret seed"))
	outDiff := make([]byte, 64)
	io.ReadFull(shakeDiff, outDiff)

	if bytes.Equal(out1, outDiff) {
		fmt.Fprintf(os.Stderr, "sha3.NewShake256 failed to produce distinct output for different input\n")
		os.Exit(1)
	}

	// 6. sha3.NewShake256 Clone produces identical output stream from cloned state
	shakeSource := sha3.NewShake256()
	shakeSource.Write([]byte("shared state data"))
	firstChunk := make([]byte, 32)
	io.ReadFull(shakeSource, firstChunk)

	shakeClone := shakeSource.Clone()

	secondChunkSource := make([]byte, 64)
	io.ReadFull(shakeSource, secondChunkSource)

	secondChunkClone := make([]byte, 64)
	io.ReadFull(shakeClone, secondChunkClone)

	if !bytes.Equal(secondChunkSource, secondChunkClone) {
		fmt.Fprintf(os.Stderr, "sha3.NewShake256 Clone stream output mismatch\n")
		os.Exit(1)
	}

	// 7. sha3.NewShake256 Reset restarts stream from initial state
	shakeReset := sha3.NewShake256()
	shakeReset.Write([]byte("arbitrary data"))
	dumpBuf := make([]byte, 100)
	io.ReadFull(shakeReset, dumpBuf)

	shakeReset.Reset()
	shakeReset.Write([]byte("abc"))
	resetBuf := make([]byte, 64)
	io.ReadFull(shakeReset, resetBuf)
	if !bytes.Equal(resetBuf, expectedShakeAbc) {
		fmt.Fprintf(os.Stderr, "sha3.NewShake256 Reset did not restart to initial state\n")
		os.Exit(1)
	}

	fmt.Println("All contract assertions passed.")
}