// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.


// Package ed25519 implements the Ed25519 signature algorithm. See
// https://ed25519.cr.yp.to/.
//
// These functions are also compatible with the “Ed25519” function defined in
// RFC 8032. However, unlike RFC 8032's formulation, this package's private key
// representation includes a public key suffix to make multiple signing
// operations with the same key more efficient. This package refers to the RFC
// 8032 private key as the “seed”.
package ed25519

// This code is a port of the public domain, “ref10” implementation of ed25519
// from SUPERCOP.

import (
	
	
	
	cryptorand 
	
	
	
	
)

const (
	// PublicKeySize is the size, in bytes, of public keys as used in this package.
	PublicKeySize = 32
	// PrivateKeySize is the size, in bytes, of private keys as used in this package.
	PrivateKeySize = 64
	// SignatureSize is the size, in bytes, of signatures generated and verified by this package.
	SignatureSize = 64
	// SeedSize is the size, in bytes, of private key seeds. These are the private key representations used by RFC 8032.
	SeedSize = 32
)

// PublicKey is the type of Ed25519 public keys.
type PublicKey []byte

// Any methods implemented on PublicKey might need to also be implemented on
// PrivateKey, as the latter embeds the former and will expose its methods.

// Equal reports whether pub and x have the same value.
func ( PublicKey) ( crypto.PublicKey) bool {
	,  := .(PublicKey)
	if ! {
		return false
	}
	return bytes.Equal(, )
}

// PrivateKey is the type of Ed25519 private keys. It implements crypto.Signer.
type PrivateKey []byte

// Public returns the PublicKey corresponding to priv.
func ( PrivateKey) () crypto.PublicKey {
	 := make([]byte, PublicKeySize)
	copy(, [32:])
	return PublicKey()
}

// Equal reports whether priv and x have the same value.
func ( PrivateKey) ( crypto.PrivateKey) bool {
	,  := .(PrivateKey)
	if ! {
		return false
	}
	return bytes.Equal(, )
}

// Seed returns the private key seed corresponding to priv. It is provided for
// interoperability with RFC 8032. RFC 8032's private keys correspond to seeds
// in this package.
func ( PrivateKey) () []byte {
	 := make([]byte, SeedSize)
	copy(, [:32])
	return 
}

// Sign signs the given message with priv.
// Ed25519 performs two passes over messages to be signed and therefore cannot
// handle pre-hashed messages. Thus opts.HashFunc() must return zero to
// indicate the message hasn't been hashed. This can be achieved by passing
// crypto.Hash(0) as the value for opts.
func ( PrivateKey) ( io.Reader,  []byte,  crypto.SignerOpts) ( []byte,  error) {
	if .HashFunc() != crypto.Hash(0) {
		return nil, errors.New("ed25519: cannot sign hashed message")
	}

	return Sign(, ), nil
}

// GenerateKey generates a public/private key pair using entropy from rand.
// If rand is nil, crypto/rand.Reader will be used.
func ( io.Reader) (PublicKey, PrivateKey, error) {
	if  == nil {
		 = cryptorand.Reader
	}

	 := make([]byte, SeedSize)
	if ,  := io.ReadFull(, );  != nil {
		return nil, nil, 
	}

	 := NewKeyFromSeed()
	 := make([]byte, PublicKeySize)
	copy(, [32:])

	return , , nil
}

// NewKeyFromSeed calculates a private key from a seed. It will panic if
// len(seed) is not SeedSize. This function is provided for interoperability
// with RFC 8032. RFC 8032's private keys correspond to seeds in this
// package.
func ( []byte) PrivateKey {
	// Outline the function body so that the returned key can be stack-allocated.
	 := make([]byte, PrivateKeySize)
	newKeyFromSeed(, )
	return 
}

func (,  []byte) {
	if  := len();  != SeedSize {
		panic("ed25519: bad seed length: " + strconv.Itoa())
	}

	 := sha512.Sum512()
	[0] &= 248
	[31] &= 127
	[31] |= 64

	var  edwards25519.ExtendedGroupElement
	var  [32]byte
	copy([:], [:])
	edwards25519.GeScalarMultBase(&, &)
	var  [32]byte
	.ToBytes(&)

	copy(, )
	copy([32:], [:])
}

// Sign signs the message with privateKey and returns a signature. It will
// panic if len(privateKey) is not PrivateKeySize.
func ( PrivateKey,  []byte) []byte {
	// Outline the function body so that the returned signature can be
	// stack-allocated.
	 := make([]byte, SignatureSize)
	sign(, , )
	return 
}

func (, ,  []byte) {
	if  := len();  != PrivateKeySize {
		panic("ed25519: bad private key length: " + strconv.Itoa())
	}

	 := sha512.New()
	.Write([:32])

	var , ,  [64]byte
	var  [32]byte
	.Sum([:0])
	copy([:], [:])
	[0] &= 248
	[31] &= 63
	[31] |= 64

	.Reset()
	.Write([32:])
	.Write()
	.Sum([:0])

	var  [32]byte
	edwards25519.ScReduce(&, &)
	var  edwards25519.ExtendedGroupElement
	edwards25519.GeScalarMultBase(&, &)

	var  [32]byte
	.ToBytes(&)

	.Reset()
	.Write([:])
	.Write([32:])
	.Write()
	.Sum([:0])
	var  [32]byte
	edwards25519.ScReduce(&, &)

	var  [32]byte
	edwards25519.ScMulAdd(&, &, &, &)

	copy([:], [:])
	copy([32:], [:])
}

// Verify reports whether sig is a valid signature of message by publicKey. It
// will panic if len(publicKey) is not PublicKeySize.
func ( PublicKey, ,  []byte) bool {
	if  := len();  != PublicKeySize {
		panic("ed25519: bad public key length: " + strconv.Itoa())
	}

	if len() != SignatureSize || [63]&224 != 0 {
		return false
	}

	var  edwards25519.ExtendedGroupElement
	var  [32]byte
	copy([:], )
	if !.FromBytes(&) {
		return false
	}
	edwards25519.FeNeg(&.X, &.X)
	edwards25519.FeNeg(&.T, &.T)

	 := sha512.New()
	.Write([:32])
	.Write([:])
	.Write()
	var  [64]byte
	.Sum([:0])

	var  [32]byte
	edwards25519.ScReduce(&, &)

	var  edwards25519.ProjectiveGroupElement
	var  [32]byte
	copy([:], [32:])

	// https://tools.ietf.org/html/rfc8032#section-5.1.7 requires that s be in
	// the range [0, order) in order to prevent signature malleability.
	if !edwards25519.ScMinimal(&) {
		return false
	}

	edwards25519.GeDoubleScalarMultVartime(&, &, &, &)

	var  [32]byte
	.ToBytes(&)
	return bytes.Equal([:32], [:])
}