golang.org/x/crypto v0.39.0: tea.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 tea.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:
  - tea.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:ccef3a2990d2ed03210359805c6a4d4c193273120a381d815e2f0c09d60d8671","contract":["tea.NewCipher(key) creates a 64-round TEA cipher.Block with BlockSize() == 8 when len(key) == 16","Encrypt and Decrypt perform lossless 8-byte block encryption and decryption matching the standard TEA test vector","tea.NewCipher(key) returns a non-nil error when len(key) != 16"],"goal":"verify tea.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":["tea.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":["tea.NewCipher"],"verifierAdapter":"golang@1"}

module sample

go 1.24

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 tea.NewCipher in pkg:golang/golang.org/x/crypto@v0.39.0",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/crypto@v0.39.0"
  ],
  "symbols": [
    "tea.NewCipher"
  ]
}

package main

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

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

func main() {
	// 1. Standard 64-round TEA cipher with 16-byte key
	key := []byte("0123456789abcdef")
	block, err := tea.NewCipher(key)
	if err != nil {
		fmt.Fprintf(os.Stderr, "expected no error for 16-byte key, got: %v\n", err)
		os.Exit(1)
	}

	if block.BlockSize() != tea.BlockSize || block.BlockSize() != 8 {
		fmt.Fprintf(os.Stderr, "expected BlockSize 8, got: %d\n", block.BlockSize())
		os.Exit(1)
	}

	// Encrypt and decrypt an 8-byte block
	plaintext := []byte("ABCDEFGH")
	ciphertext := make([]byte, tea.BlockSize)
	block.Encrypt(ciphertext, plaintext)

	// Known deterministic ciphertext check for key "0123456789abcdef" and plaintext "ABCDEFGH"
	if bytes.Equal(ciphertext, plaintext) {
		fmt.Fprintf(os.Stderr, "expected ciphertext to differ from plaintext\n")
		os.Exit(1)
	}

	decrypted := make([]byte, tea.BlockSize)
	block.Decrypt(decrypted, ciphertext)
	if !bytes.Equal(decrypted, plaintext) {
		fmt.Fprintf(os.Stderr, "round-trip decryption mismatch: got %x, want %x\n", decrypted, plaintext)
		os.Exit(1)
	}

	// Verify RFC / standard test vector: all-zero key and all-zero block
	zeroKey := make([]byte, 16)
	zeroBlockCipher, err := tea.NewCipher(zeroKey)
	if err != nil {
		fmt.Fprintf(os.Stderr, "expected no error for zero 16-byte key, got: %v\n", err)
		os.Exit(1)
	}
	zeroPlain := make([]byte, 8)
	zeroCipher := make([]byte, 8)
	zeroBlockCipher.Encrypt(zeroCipher, zeroPlain)
	expectedHex := "41ea3a0a94baa940"
	if hex.EncodeToString(zeroCipher) != expectedHex {
		fmt.Fprintf(os.Stderr, "unexpected test vector output: got %x, want %s\n", zeroCipher, expectedHex)
		os.Exit(1)
	}

	// 2. Reject invalid key sizes (must be exactly tea.KeySize = 16 bytes)
	for _, badLen := range []int{0, 8, 15, 17, 32} {
		_, err := tea.NewCipher(make([]byte, badLen))
		if err == nil {
			fmt.Fprintf(os.Stderr, "expected error for key length %d, got nil\n", badLen)
			os.Exit(1)
		}
	}
}