golang.org/x/crypto v0.39.0: xtea.NewCipher

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 xtea.NewCipher in pkg:golang/golang.org/x/crypto@v0.39.0
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/crypto@v0.39.0
Demonstrate these symbols/APIs:
  - xtea.NewCipher

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:sha256:56e1ccf87ecde0521402833daeb276714dba6fa4c96f131b58b68b08135f3b00","contract":["xtea.NewCipher accepts a 16-byte key and returns a block cipher with BlockSize 8","Encrypt and Decrypt round-trip an 8-byte block back to the original plaintext","xtea.NewCipher returns xtea.KeySizeError when given a key whose length is not 16 bytes"],"goal":"verify xtea.NewCipher in pkg:golang/golang.org/x/crypto@v0.39.0","kind":"HOW","packages":["pkg:golang/golang.org/x/crypto@v0.39.0"],"schemaVersion":1,"symbols":["xtea.NewCipher"]},"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@v0.39.0"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/crypto@v0.39.0","symbols":["xtea.NewCipher"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.23.0

require golang.org/x/crypto v0.39.0

golang.org/x/crypto v0.39.0 h1:SHs+kF4LP+f+p14esP5jAoDpHU8Gu/v9lFRK6IT5imM=
golang.org/x/crypto v0.39.0/go.mod h1:L+Xg3Wf6HoL4Bn4238Z6ft6KfEpN0tJGo53AAPC632U=

{
  "schemaVersion": 1,
  "goal": "verify xtea.NewCipher in pkg:golang/golang.org/x/crypto@v0.39.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/crypto@v0.39.0"
  ],
  "symbols": [
    "xtea.NewCipher"
  ]
}

package main

import (
	"bytes"
	"errors"
	"fmt"
	"os"

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

func main() {
	key := []byte("0123456789abcdef")
	cipher, err := xtea.NewCipher(key)
	if err != nil {
		fmt.Fprintf(os.Stderr, "unexpected error from NewCipher: %v\n", err)
		os.Exit(1)
	}

	if cipher.BlockSize() != xtea.BlockSize || xtea.BlockSize != 8 {
		fmt.Fprintf(os.Stderr, "unexpected block size: got %d, want 8\n", cipher.BlockSize())
		os.Exit(1)
	}

	plaintext := []byte("8byteblk")
	ciphertext := make([]byte, xtea.BlockSize)
	cipher.Encrypt(ciphertext, plaintext)

	if bytes.Equal(ciphertext, plaintext) {
		fmt.Fprintln(os.Stderr, "ciphertext matches plaintext")
		os.Exit(1)
	}

	decrypted := make([]byte, xtea.BlockSize)
	cipher.Decrypt(decrypted, ciphertext)

	if !bytes.Equal(decrypted, plaintext) {
		fmt.Fprintf(os.Stderr, "decrypted %q != plaintext %q\n", decrypted, plaintext)
		os.Exit(1)
	}

	_, shortErr := xtea.NewCipher([]byte("short"))
	var keySizeErr xtea.KeySizeError
	if !errors.As(shortErr, &keySizeErr) || keySizeErr != xtea.KeySizeError(5) {
		fmt.Fprintf(os.Stderr, "expected KeySizeError(5), got %v\n", shortErr)
		os.Exit(1)
	}
}