1package ownrsa
  2
  3import (
  4	"errors"
  5	"fmt"
  6	"math/big"
  7	"math/rand"
  8	"strconv"
  9	"strings"
 10	"time"
 11)
 12
 13type RSAPublicKey struct {
 14	E *big.Int `json:"e"`
 15	N *big.Int `json:"n"`
 16}
 17type RSAPublicKeyString struct {
 18	E string `json:"e"`
 19	N string `json:"n"`
 20}
 21type RSAPrivateKey struct {
 22	D *big.Int `json:"d"`
 23	N *big.Int `json:"n"`
 24}
 25
 26type RSA struct {
 27	PubK  RSAPublicKey
 28	PrivK RSAPrivateKey
 29}
 30
 31type PackRSA struct {
 32	PubK       string    `json:"pubK"`
 33	PrivK      string    `json:"privK"`
 34	Date       time.Time `json:"date"`
 35	PubKSigned string    `json:"pubKSigned"`
 36}
 37
 38const maxPrime = 500
 39const minPrime = 100
 40
 41func GenerateKeyPair() RSA {
 42
 43	rand.Seed(time.Now().Unix())
 44	p := randPrime(minPrime, maxPrime)
 45	q := randPrime(minPrime, maxPrime)
 46	fmt.Print("p:")
 47	fmt.Println(p)
 48	fmt.Print("q:")
 49	fmt.Println(q)
 50
 51	n := p * q
 52	phi := (p - 1) * (q - 1)
 53	e := 65537
 54	var pubK RSAPublicKey
 55	pubK.E = big.NewInt(int64(e))
 56	pubK.N = big.NewInt(int64(n))
 57
 58	d := new(big.Int).ModInverse(big.NewInt(int64(e)), big.NewInt(int64(phi)))
 59
 60	var privK RSAPrivateKey
 61	privK.D = d
 62	privK.N = big.NewInt(int64(n))
 63
 64	var rsa RSA
 65	rsa.PubK = pubK
 66	rsa.PrivK = privK
 67	return rsa
 68}
 69func Encrypt(m string, pubK RSAPublicKey) []int {
 70	var c []int
 71	mBytes := []byte(m)
 72	for _, byte := range mBytes {
 73		c = append(c, EncryptInt(int(byte), pubK))
 74	}
 75	return c
 76}
 77func Decrypt(c []int, privK RSAPrivateKey) string {
 78	var m string
 79	var mBytes []byte
 80	for _, indC := range c {
 81		mBytes = append(mBytes, byte(DecryptInt(indC, privK)))
 82	}
 83	m = string(mBytes)
 84	return m
 85}
 86
 87func EncryptBigInt(bigint *big.Int, pubK RSAPublicKey) *big.Int {
 88	Me := new(big.Int).Exp(bigint, pubK.E, nil)
 89	c := new(big.Int).Mod(Me, pubK.N)
 90	return c
 91}
 92func DecryptBigInt(bigint *big.Int, privK RSAPrivateKey) *big.Int {
 93	Cd := new(big.Int).Exp(bigint, privK.D, nil)
 94	m := new(big.Int).Mod(Cd, privK.N)
 95	return m
 96}
 97
 98func EncryptInt(char int, pubK RSAPublicKey) int {
 99	charBig := big.NewInt(int64(char))
100	Me := charBig.Exp(charBig, pubK.E, nil)
101	c := Me.Mod(Me, pubK.N)
102	return int(c.Int64())
103}
104func DecryptInt(val int, privK RSAPrivateKey) int {
105	valBig := big.NewInt(int64(val))
106	Cd := valBig.Exp(valBig, privK.D, nil)
107	m := Cd.Mod(Cd, privK.N)
108	return int(m.Int64())
109}
110
111func Blind(m []int, r int, pubK RSAPublicKey, privK RSAPrivateKey) []int {
112	var mBlinded []int
113	rBigInt := big.NewInt(int64(r))
114	for i := 0; i < len(m); i++ {
115		mBigInt := big.NewInt(int64(m[i]))
116		rE := new(big.Int).Exp(rBigInt, pubK.E, nil)
117		mrE := new(big.Int).Mul(mBigInt, rE)
118		mrEmodN := new(big.Int).Mod(mrE, privK.N)
119		mBlinded = append(mBlinded, int(mrEmodN.Int64()))
120	}
121	return mBlinded
122}
123
124func BlindSign(m []int, privK RSAPrivateKey) []int {
125	var r []int
126	for i := 0; i < len(m); i++ {
127		mBigInt := big.NewInt(int64(m[i]))
128		sigma := new(big.Int).Exp(mBigInt, privK.D, privK.N)
129		r = append(r, int(sigma.Int64()))
130	}
131	return r
132}
133func Unblind(blindsigned []int, r int, pubK RSAPublicKey) []int {
134	var mSigned []int
135	rBigInt := big.NewInt(int64(r))
136	for i := 0; i < len(blindsigned); i++ {
137		bsBigInt := big.NewInt(int64(blindsigned[i]))
138		//r1 := new(big.Int).Exp(rBigInt, big.NewInt(int64(-1)), nil)
139		r1 := new(big.Int).ModInverse(rBigInt, pubK.N)
140		bsr := new(big.Int).Mul(bsBigInt, r1)
141		sig := new(big.Int).Mod(bsr, pubK.N)
142		mSigned = append(mSigned, int(sig.Int64()))
143	}
144	return mSigned
145}
146func Verify(msg []int, mSigned []int, pubK RSAPublicKey) bool {
147	if len(msg) != len(mSigned) {
148		return false
149	}
150	var mSignedDecrypted []int
151	for _, ms := range mSigned {
152		msBig := big.NewInt(int64(ms))
153		//decrypt the mSigned with pubK
154		Cd := new(big.Int).Exp(msBig, pubK.E, nil)
155		m := new(big.Int).Mod(Cd, pubK.N)
156		mSignedDecrypted = append(mSignedDecrypted, int(m.Int64()))
157	}
158	fmt.Print("msg signed decrypted: ")
159	fmt.Println(mSignedDecrypted)
160	r := true
161	//check if the mSignedDecrypted == msg
162	for i := 0; i < len(msg); i++ {
163		if msg[i] != mSignedDecrypted[i] {
164			r = false
165		}
166	}
167	return r
168}
169
170func HomomorphicMultiplication(c1 int, c2 int, pubK RSAPublicKey) int {
171	c1BigInt := big.NewInt(int64(c1))
172	c2BigInt := big.NewInt(int64(c2))
173	c1c2 := new(big.Int).Mul(c1BigInt, c2BigInt)
174	n2 := new(big.Int).Mul(pubK.N, pubK.N)
175	d := new(big.Int).Mod(c1c2, n2)
176	r := int(d.Int64())
177	return r
178}
179
180func PubKStringToBigInt(kS RSAPublicKeyString) (RSAPublicKey, error) {
181	var k RSAPublicKey
182	var ok bool
183	k.E, ok = new(big.Int).SetString(kS.E, 10)
184	if !ok {
185		return k, errors.New("error parsing big int E")
186	}
187	k.N, ok = new(big.Int).SetString(kS.N, 10)
188	if !ok {
189		return k, errors.New("error parsing big int N")
190	}
191	return k, nil
192}
193
194func PackKey(k RSA) PackRSA {
195	var p PackRSA
196	p.PubK = k.PubK.E.String() + "," + k.PubK.N.String()
197	p.PrivK = k.PrivK.D.String() + "," + k.PrivK.N.String()
198	return p
199}
200
201func UnpackKey(p PackRSA) RSA {
202	var k RSA
203	var ok bool
204	k.PubK.E, ok = new(big.Int).SetString(strings.Split(p.PubK, ",")[0], 10)
205	k.PubK.N, ok = new(big.Int).SetString(strings.Split(p.PubK, ",")[1], 10)
206	k.PrivK.D, ok = new(big.Int).SetString(strings.Split(p.PrivK, ",")[0], 10)
207	k.PrivK.N, ok = new(big.Int).SetString(strings.Split(p.PrivK, ",")[1], 10)
208	if !ok {
209		fmt.Println("error on Unpacking Keys")
210	}
211	return k
212}
213
214func ArrayIntToString(a []int, delim string) string {
215	return strings.Trim(strings.Replace(fmt.Sprint(a), " ", delim, -1), "[]")
216}
217func StringToArrayInt(s string, delim string) []int {
218	var a []int
219	arrayString := strings.Split(s, delim)
220	for _, s := range arrayString {
221		i, err := strconv.Atoi(s)
222		if err != nil {
223			fmt.Println(err)
224		}
225		a = append(a, i)
226	}
227	return a
228}