EllipticCurve
An elliptic curve library written in Swift 4
Warning: this library started as a learning process. It is not meant for production use. Please use libsecp256k1 instead.
Features
 [x] ECDSA
 [x] secp256k1
 [x] provide your own hashing functions
 [x] FiniteFieldInteger protocol to create your own finite field integers
 [x] EllipticCurve protocol to create your own elliptic curves
 [x] generic signing and signature verifying
 [x] secp192k1, secp192r1, secp224k1, secp224r1, secp256k1, secp256r1
CREATE YOUR OWN ELLIPTIC CURVES! :smiley:
This Library provides the necessary scaffoldings for you to easily create elliptic curves.
The library includes several SEC2 curves,
among which is the secp256k1
, the most
popular curve at the moment. On top of the curves, a generic
ECDSA struct is included for signing and verifying.
Protocol oriented architecture
All the protocols are generic, which means none of them is tied to a certain curve or a specific UInt family member. It is very straight forward to create a specific finite field with a specific prime number as its order, or to create a specific elliptic curve of Double precision or Float80 precision. Please see to the playground for demonstrations.
The top level protocol for creating elliptic curve cryptography is EllipticCurveOverFiniteField. It is constructed from two basic protocols: FiniteFieldInteger and EllipticCurve, the former of which is based on FiniteField. The diagram of protocol inheritance is as follows:
++
 
 FiniteField +
  
++ Conformance
 
Conformance 
 
+v+  ++
    
 FiniteFieldInteger    EllipticCurve 
    
++  ++
  
  
As Coordinates ++ Conformance
   
+ EllipticCurveOverFiniteField <+
 
++

As T

++
 
 ECDSA<T> 
 
++
FiniteField
FiniteField is the base protocol.
It defines several basic properties like Zero
,
One
, Characteristic
, and etc. It is not meant
to be used directly, but you can use it to create
finite fields.
FiniteFieldInteger
FiniteFieldInteger defines the basic scaffolding and provides most of the default implementations for any finite field integer. Example:
let p: UInt8 = 223
struct MyFFInt: FiniteFieldInteger {
static var Characteristic = p
var value: UInt8
init() {
value = 0
}
}
let a: MyFFInt = 1
let b: MyFFInt = 500
print(a + b)
This will create a finite field integer of F_223, and then you can use the basic +, , *, / on it.
EllipticCurve
EllipticCurve is also generic. You can create an elliptic curve on real domain like this:
struct MyECPoint: EllipticCurve {
static var a: Double = 1
static var b: Double = 1
var x: Double
var y: Double?
init() {
x = 0
}
}
let p: MyECPoint = MyECPoint(x: 1, y: 1)
print(p.description)
EllipticCurveOverFiniteField
This is the top level protocol to use, if you want to create an ECC of your own:
let P: UInt8 = 223
struct FFInt223: FiniteFieldInteger {
static var Characteristic: UInt8 = P
var value: UInt8
init() {
value = 0
}
}
struct MyECFF: EllipticCurveOverFiniteField {
static var Order: UInt8 = 212
static var a: FFInt223 = 2
static var b: FFInt223 = 7
var x: FFInt223
var y: FFInt223?
static var Generator: MyECFF = MyECFF(x: 16, y: 11)
init() {
x = 0
}
}
Requirements
 iOS 8.0+ / macOS 10.10+
 Xcode 9.2+
 Swift 4
Installation
Carthage
Currently, only carthage package installation is tested.
 install Carthage:
brew install carthage
 add this line to your Cartfile:
github "hyugit/EllipticCurve"
 run
carthage update
under your project directory
Swift Package Manager
dependencies: [
.package(url: "https://github.com/hyugit/EllipticCurve.git", from: "0.3.0")
]
Communication
If you have a bug report or a feature request, please open an issue here on GitHub. Any contribution is welcome. :smiley:
License
EllipticCurve is released under MIT license. See LICENSE for details.