golang.org/x/crypto v0.0.0-20190426145343-a29dc8fdc734: ed25519.Sign

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 golang.org/x/crypto/ed25519.Sign in pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734
Demonstrate these symbols/APIs:
  - golang.org/x/crypto/ed25519.Sign

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:f7f86bfd5399ec1d1334009f6fc9bd5a9d03ae44a6eba31952e45f22f84bfa21","contract":["ed25519.Sign(privateKey, message) returns a 64-byte signature that passes ed25519.Verify with the corresponding PublicKey","ed25519.Sign is deterministic for the same privateKey and message","ed25519.Sign panics when len(privateKey) != ed25519.PrivateKeySize"],"goal":"verify golang.org/x/crypto/ed25519.Sign in pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734","kind":"HOW","packages":["pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734"],"schemaVersion":1,"symbols":["golang.org/x/crypto/ed25519.Sign"]},"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@v0.0.0-20190426145343-a29dc8fdc734"],"schemaVersion":1,"subject":"pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734","symbols":["golang.org/x/crypto/ed25519.Sign"],"verifierAdapter":"golang@1"}

module example.com/sample

go 1.18

require golang.org/x/crypto v0.0.0-20190426145343-a29dc8fdc734

golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/crypto v0.0.0-20190426145343-a29dc8fdc734 h1:p/H982KKEjUnLJkM3tt/LemDnOc1GiZL5FCVlORJ5zo=
golang.org/x/crypto v0.0.0-20190426145343-a29dc8fdc734/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=

{
  "schemaVersion": 1,
  "goal": "verify golang.org/x/crypto/ed25519.Sign in pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734",
  "kind": "HOW",
  "packages": [
    "pkg:golang/golang.org/x/crypto@v0.0.0-20190426145343-a29dc8fdc734"
  ],
  "symbols": [
    "golang.org/x/crypto/ed25519.Sign"
  ]
}

package main

import (
	"bytes"
	"os"

	"golang.org/x/crypto/ed25519"
)

func main() {
	seed := bytes.Repeat([]byte{0x42}, ed25519.SeedSize)
	priv := ed25519.NewKeyFromSeed(seed)
	pub := priv.Public().(ed25519.PublicKey)

	msg := []byte("sample message for ed25519 signing")
	sig := ed25519.Sign(priv, msg)

	if len(sig) != ed25519.SignatureSize {
		os.Exit(1)
	}
	if !ed25519.Verify(pub, msg, sig) {
		os.Exit(1)
	}
	if ed25519.Verify(pub, []byte("tampered"), sig) {
		os.Exit(1)
	}

	// Deterministic signing: signing the same message with the same private key yields identical signature
	sig2 := ed25519.Sign(priv, msg)
	if !bytes.Equal(sig, sig2) {
		os.Exit(1)
	}

	// Wrong private key length panics
	panicked := false
	func() {
		defer func() {
			if recover() != nil {
				panicked = true
			}
		}()
		ed25519.Sign(ed25519.PrivateKey([]byte("short")), msg)
	}()
	if !panicked {
		os.Exit(1)
	}
}