nim-libp2p-experimental/libp2p/crypto/secp.nim

## Nim-Libp2p
## Copyright (c) 2018 Status Research & Development GmbH
## Licensed under either of
##  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
##  * MIT license ([LICENSE-MIT](LICENSE-MIT))
## at your option.
## This file may not be copied, modified, or distributed except according to
## those terms.

{.push raises: [Defect].}

import secp256k1, stew/byteutils, nimcrypto/hash, nimcrypto/sha2
export sha2
import stew/results

export results
export secp256k1

const
  SkRawPrivateKeySize* = 256 div 8
    ## Size of private key in octets (bytes)
  SkRawSignatureSize* = SkRawPrivateKeySize * 2 + 1
    ## Size of signature in octets (bytes)
  SkRawPublicKeySize* = SkRawPrivateKeySize + 1
    ## Size of public key in octets (bytes)

type
  SkPrivateKey* = SkSecretKey

template pubkey*(v: SkKeyPair): SkPublicKey = SkPublicKey(SkKeyPair(v).pubkey)
template seckey*(v: SkKeyPair): SkPrivateKey = SkPrivateKey(SkKeyPair(v).seckey)

proc init*(key: var SkPrivateKey, data: openarray[byte]): SkResult[void] =
  ## Initialize Secp256k1 `private key` ``key`` from raw binary
  ## representation ``data``.
  key = ? SkSecretKey.fromRaw(data)
  ok()

proc init*(key: var SkPrivateKey, data: string): SkResult[void] =
  ## Initialize Secp256k1 `private key` ``key`` from hexadecimal string
  ## representation ``data``.
  key = ? SkSecretKey.fromHex(data)
  ok()

proc init*(key: var SkPublicKey, data: openarray[byte]): SkResult[void] =
  ## Initialize Secp256k1 `public key` ``key`` from raw binary
  ## representation ``data``.
  key = ? SkPublicKey.fromRaw(data)
  ok()

proc init*(key: var SkPublicKey, data: string): SkResult[void] =
  ## Initialize Secp256k1 `public key` ``key`` from hexadecimal string
  ## representation ``data``.
  key = ? SkPublicKey.fromHex(data)
  ok()

proc init*(sig: var SkSignature, data: openarray[byte]): SkResult[void] =
  ## Initialize Secp256k1 `signature` ``sig`` from raw binary
  ## representation ``data``.
  sig = ? SkSignature.fromDer(data)
  ok()

proc init*(sig: var SkSignature, data: string): SkResult[void] =
  ## Initialize Secp256k1 `signature` ``sig`` from hexadecimal string
  ## representation ``data``.
  # TODO DER vs raw here is fishy
  var buffer: seq[byte]
  try:
    buffer = hexToSeqByte(data)
  except ValueError:
    return err("Hex to bytes failed")
  init(sig, buffer)

proc init*(t: typedesc[SkPrivateKey], data: openarray[byte]): SkResult[SkPrivateKey] =
  ## Initialize Secp256k1 `private key` from raw binary
  ## representation ``data``.
  ##
  ## Procedure returns `private key` on success.
  SkSecretKey.fromRaw(data)

proc init*(t: typedesc[SkPrivateKey], data: string): SkResult[SkPrivateKey] =
  ## Initialize Secp256k1 `private key` from hexadecimal string
  ## representation ``data``.
  ##
  ## Procedure returns `private key` on success.
  SkSecretKey.fromHex(data)

proc init*(t: typedesc[SkPublicKey], data: openarray[byte]): SkResult[SkPublicKey] =
  ## Initialize Secp256k1 `public key` from raw binary
  ## representation ``data``.
  ##
  ## Procedure returns `public key` on success.
  var key: SkPublicKey
  key.init(data) and ok(key)

proc init*(t: typedesc[SkPublicKey], data: string): SkResult[SkPublicKey] =
  ## Initialize Secp256k1 `public key` from hexadecimal string
  ## representation ``data``.
  ##
  ## Procedure returns `public key` on success.
  var key: SkPublicKey
  key.init(data) and ok(key)

proc init*(t: typedesc[SkSignature], data: openarray[byte]): SkResult[SkSignature] =
  ## Initialize Secp256k1 `signature` from raw binary
  ## representation ``data``.
  ##
  ## Procedure returns `signature` on success.
  var sig: SkSignature
  sig.init(data) and ok(sig)

proc init*(t: typedesc[SkSignature], data: string): SkResult[SkSignature] =
  ## Initialize Secp256k1 `signature` from hexadecimal string
  ## representation ``data``.
  ##
  ## Procedure returns `signature` on success.
  var sig: SkSignature
  sig.init(data) and ok(sig)

proc getKey*(key: SkPrivateKey): SkResult[SkPublicKey] =
  ## Calculate and return Secp256k1 `public key` from `private key` ``key``.
  key.toPublicKey()

proc toBytes*(key: SkPrivateKey, data: var openarray[byte]): SkResult[int] =
  ## Serialize Secp256k1 `private key` ``key`` to raw binary form and store it
  ## to ``data``.
  ##
  ## Procedure returns number of bytes (octets) needed to store
  ## Secp256k1 private key.
  if len(data) >= SkRawPrivateKeySize:
    data[0..<SkRawPrivateKeySize] = SkSecretKey(key).toRaw()
    ok(SkRawPrivateKeySize)
  else:
    err("Not enough bytes")

proc toBytes*(key: SkPublicKey, data: var openarray[byte]): SkResult[int] =
  ## Serialize Secp256k1 `public key` ``key`` to raw binary form and store it
  ## to ``data``.
  ##
  ## Procedure returns number of bytes (octets) needed to store
  ## Secp256k1 public key.
  if len(data) >= SkRawPublicKeySize:
    data[0..<SkRawPublicKeySize] = key.toRawCompressed()
    ok(SkRawPublicKeySize)
  else:
    err("Not enough bytes")

proc toBytes*(sig: SkSignature, data: var openarray[byte]): int =
  ## Serialize Secp256k1 `signature` ``sig`` to raw binary form and store it
  ## to ``data``.
  ##
  ## Procedure returns number of bytes (octets) needed to store
  ## Secp256k1 signature.
  sig.toDer(data)

proc getBytes*(key: SkPrivateKey): seq[byte] {.inline.} =
  ## Serialize Secp256k1 `private key` and return it.
  result = @(SkSecretKey(key).toRaw())

proc getBytes*(key: SkPublicKey): seq[byte] {.inline.} =
  ## Serialize Secp256k1 `public key` and return it.
  result = @(key.toRawCompressed())

proc getBytes*(sig: SkSignature): seq[byte] {.inline.} =
  ## Serialize Secp256k1 `signature` and return it.
  result = newSeq[byte](72)
  let length = toBytes(sig, result)
  result.setLen(length)

proc sign*[T: byte|char](key: SkPrivateKey, msg: openarray[T]): SkResult[SkSignature] =
  ## Sign message `msg` using private key `key` and return signature object.
  let h = sha256.digest(msg)
  sign(key, h)

proc verify*[T: byte|char](sig: SkSignature, msg: openarray[T],
                           key: SkPublicKey): bool =
  let h = sha256.digest(msg)
  verify(SkSignature(sig), h, SkPublicKey(key))