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ecdh.swift
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ecdh.swift
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/*
Copyright (C) 2019 MIRACL UK Ltd.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU Affero General Public License as
published by the Free Software Foundation, either version 3 of the
License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU Affero General Public License for more details.
https://www.gnu.org/licenses/agpl-3.0.en.html
You should have received a copy of the GNU Affero General Public License
along with this program. If not, see <https://www.gnu.org/licenses/>.
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
You can be released from the requirements of the license by purchasing
a commercial license. Buying such a license is mandatory as soon as you
develop commercial activities involving the MIRACL Core Crypto SDK
without disclosing the source code of your own applications, or shipping
the MIRACL Core Crypto SDK with a closed source product.
*/
//
// ecdh.swift
//
// Created by Michael Scott on 30/06/2015.
// Copyright (c) 2015 Michael Scott. All rights reserved.
//
//import Foundation
//import Darwin
import core
/* Elliptic Curve API high-level functions */
public struct ECDH
{
static let INVALID_PUBLIC_KEY:Int = -2
static let ERROR:Int = -3
//static let INVALID:Int = -4
static public let EFS=Int(CONFIG_BIG.MODBYTES);
static public let EGS=Int(CONFIG_BIG.MODBYTES);
static public let SHA256=32
static public let SHA384=48
static public let SHA512=64
/* Calculate a public/private EC GF(p) key pair W,S where W=S.G mod EC(p),
* where S is the secret key and W is the public key
* and G is fixed generator.
* If RNG is NULL then the private key is provided externally in S
* otherwise it is generated randomly internally */
@discardableResult static public func KEY_PAIR_GENERATE(_ RNG: inout RAND?,_ S:inout [UInt8],_ W:inout [UInt8]) -> Int
{
let res=0;
var s:BIG
var G:ECP
G=ECP.generator();
let r=BIG(ROM.CURVE_Order)
if (RNG==nil)
{
s=BIG.fromBytes(S)
s.mod(r)
}
else
{
s=BIG.randtrunc(r,16*CONFIG_CURVE.AESKEY,&RNG!)
}
s.toBytes(&S)
let WP=G.mul(s)
WP.toBytes(&W,false) // To use point compression on public keys, change to true
return res;
}
/* validate public key */
static public func PUBLIC_KEY_VALIDATE(_ W:[UInt8]) -> Int
{
var WP=ECP.fromBytes(W);
var res=0;
let r=BIG(ROM.CURVE_Order)
if WP.is_infinity() {res=INVALID_PUBLIC_KEY}
if res==0
{
let q=BIG(ROM.Modulus)
let nb=UInt(q.nbits())
var k=BIG(1); k.shl((nb+4)/2)
k.add(q)
k.div(r)
while k.parity()==0 {
k.shr(1)
WP.dbl()
}
if !k.isunity() {WP=WP.mul(k)}
if WP.is_infinity() {res=INVALID_PUBLIC_KEY}
}
return res;
}
/* IEEE-1363 Diffie-Hellman online calculation Z=S.WD */
@discardableResult static public func ECPSVDP_DH(_ S:[UInt8],_ WD:[UInt8],_ Z:inout [UInt8]) -> Int
{
var res=0
var T=[UInt8](repeating: 0,count: ECDH.EFS)
var s=BIG.fromBytes(S)
var W=ECP.fromBytes(WD)
if W.is_infinity() {res=ECDH.ERROR}
if (res==0)
{
let r=BIG(ROM.CURVE_Order)
s.mod(r)
W=W.mul(s);
if W.is_infinity() {res=ECDH.ERROR}
else
{
W.getX().toBytes(&T);
for i in 0 ..< ECDH.EFS {Z[i]=T[i]}
}
}
return res;
}
/* IEEE ECDSA Signature, C and D are signature on F using private key S */
static public func ECPSP_DSA(_ sha:Int,_ RNG: inout RAND,_ S:[UInt8],_ F:[UInt8],_ C:inout [UInt8],_ D:inout [UInt8]) -> Int
{
var T=[UInt8](repeating: 0,count: ECDH.EFS)
let B=HMAC.GPhashit(HMAC.MC_SHA2,sha,Int(CONFIG_BIG.MODBYTES), F,-1,nil)
let G=ECP.generator();
let r=BIG(ROM.CURVE_Order)
let s=BIG.fromBytes(S)
let f=BIG.fromBytes(B)
var c=BIG(0)
var d=BIG(0)
var V=ECP()
repeat {
var u=BIG.randomnum(r,&RNG);
let w=BIG.randomnum(r,&RNG); /* side channel masking */
V.copy(G)
V=V.mul(u)
let vx=V.getX()
c.copy(vx)
c.mod(r)
if c.iszilch() {continue}
u.copy(BIG.modmul(u,w,r))
u.invmodp(r)
d.copy(BIG.modmul(s,c,r))
d.add(f)
d.copy(BIG.modmul(d,w,r))
d.copy(BIG.modmul(u,d,r))
} while d.iszilch()
c.toBytes(&T)
for i in 0 ..< ECDH.EFS {C[i]=T[i]}
d.toBytes(&T)
for i in 0 ..< ECDH.EFS {D[i]=T[i]}
return 0;
}
/* IEEE1363 ECDSA Signature Verification. Signature C and D on F is verified using public key W */
static public func ECPVP_DSA(_ sha:Int,_ W:[UInt8],_ F:[UInt8],_ C:[UInt8],_ D:[UInt8]) -> Int
{
var res=0
let B=HMAC.GPhashit(HMAC.MC_SHA2,sha,Int(CONFIG_BIG.MODBYTES),F,-1,nil)
let G=ECP.generator();
let r=BIG(ROM.CURVE_Order)
let c=BIG.fromBytes(C)
var d=BIG.fromBytes(D)
var f=BIG.fromBytes(B)
if c.iszilch() || BIG.comp(c,r)>=0 || d.iszilch() || BIG.comp(d,r)>=0
{res=ECDH.ERROR}
if res==0
{
d.invmodp(r);
f.copy(BIG.modmul(f,d,r))
let h2=BIG.modmul(c,d,r)
let WP=ECP.fromBytes(W)
if WP.is_infinity() {res=ECDH.ERROR}
else
{
var P=ECP();
P.copy(WP);
P=P.mul2(h2,G,f);
if P.is_infinity() {res=ECDH.ERROR}
else
{
d=P.getX();
d.mod(r);
if (BIG.comp(d,c) != 0) {res=ECDH.ERROR}
}
}
}
return res;
}
/* IEEE1363 ECIES encryption. Encryption of plaintext M uses public key W and produces ciphertext V,C,T */
static public func ECIES_ENCRYPT(_ sha:Int,_ P1:[UInt8],_ P2:[UInt8],_ RNG: inout RAND?,_ W:[UInt8],_ M:[UInt8],_ V:inout [UInt8],_ T:inout [UInt8]) -> [UInt8]
{
var Z=[UInt8](repeating: 0,count: ECDH.EFS)
var VZ=[UInt8](repeating: 0,count: 3*ECDH.EFS+1)
var K1=[UInt8](repeating: 0,count: CONFIG_CURVE.AESKEY)
var K2=[UInt8](repeating: 0,count: CONFIG_CURVE.AESKEY)
var U=[UInt8](repeating: 0,count: ECDH.EGS)
if ECDH.KEY_PAIR_GENERATE(&RNG,&U,&V) != 0 {return [UInt8]()}
if ECDH.ECPSVDP_DH(U,W,&Z) != 0 {return [UInt8]()}
for i in 0 ..< 2*ECDH.EFS+1 {VZ[i]=V[i]}
for i in 0 ..< ECDH.EFS {VZ[2*ECDH.EFS+1+i]=Z[i]}
let K=HMAC.KDF2(HMAC.MC_SHA2,sha,VZ,P1,2*CONFIG_CURVE.AESKEY)
for i in 0 ..< CONFIG_CURVE.AESKEY {K1[i]=K[i]; K2[i]=K[CONFIG_CURVE.AESKEY+i];}
let C=AES.CBC_IV0_ENCRYPT(K1,M)
let L2=HMAC.inttoBytes(P2.count,8)
var AC=[UInt8](repeating: 0,count: C.count+P2.count+8)
for i in 0 ..< C.count {AC[i]=C[i]}
for i in 0 ..< P2.count {AC[C.count+i]=P2[i]}
for i in 0 ..< 8 {AC[C.count+P2.count+i]=L2[i]}
HMAC.HMAC1(HMAC.MC_SHA2,sha,&T,T.count,K2,AC)
return C
}
/* constant time n-byte compare */
static func ncomp(_ T1:[UInt8],_ T2:[UInt8],_ n:Int) -> Bool {
var res=0
for i in 0 ..< n {
res|=Int(T1[i]^T2[i])
}
if res==0 {return true}
return false
}
/* IEEE1363 ECIES decryption. Decryption of ciphertext V,C,T using private key U outputs plaintext M */
static public func ECIES_DECRYPT(_ sha:Int,_ P1:[UInt8],_ P2:[UInt8],_ V:[UInt8],_ C:[UInt8],_ T:[UInt8],_ U:[UInt8]) -> [UInt8]
{
var Z=[UInt8](repeating: 0,count: ECDH.EFS)
var VZ=[UInt8](repeating: 0,count: 3*ECDH.EFS+1)
var K1=[UInt8](repeating: 0,count: CONFIG_CURVE.AESKEY)
var K2=[UInt8](repeating: 0,count: CONFIG_CURVE.AESKEY)
var TAG=[UInt8](repeating: 0,count: T.count)
if ECPSVDP_DH(U,V,&Z) != 0 {return [UInt8]()}
for i in 0 ..< 2*ECDH.EFS+1 {VZ[i]=V[i]}
for i in 0 ..< ECDH.EFS {VZ[2*EFS+1+i]=Z[i]}
let K=HMAC.KDF2(HMAC.MC_SHA2,sha,VZ,P1,2*CONFIG_CURVE.AESKEY)
for i in 0 ..< CONFIG_CURVE.AESKEY {K1[i]=K[i]; K2[i]=K[CONFIG_CURVE.AESKEY+i]}
let M=AES.CBC_IV0_DECRYPT(K1,C)
if M.count==0 {return M}
let L2=HMAC.inttoBytes(P2.count,8)
var AC=[UInt8](repeating: 0,count: C.count+P2.count+8)
for i in 0 ..< C.count {AC[i]=C[i]}
for i in 0 ..< P2.count {AC[C.count+i]=P2[i]}
for i in 0 ..< 8 {AC[C.count+P2.count+i]=L2[i]}
HMAC.HMAC1(HMAC.MC_SHA2,sha,&TAG,TAG.count,K2,AC)
if !ncomp(T,TAG,T.count) {return [UInt8]()}
return M;
}
}