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Consume IBE hash function from the suite #34

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merged 5 commits into from
Aug 3, 2022
Merged

Consume IBE hash function from the suite #34

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7f74eab
Consume IBE hash function from the suite
CluEleSsUK Aug 3, 2022
74c2d65
Updated from PR comments
CluEleSsUK Aug 3, 2022
bd91dd8
removed mentions of xof in text
CluEleSsUK Aug 3, 2022
ce5cbcb
patching newly discovered race condition with a mutex in StatusMatrix
AnomalRoil Aug 3, 2022
bc98c41
adding xorSigma length test
AnomalRoil Aug 3, 2022
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59 changes: 31 additions & 28 deletions encrypt/ibe/ibe.go
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Original file line number Diff line number Diff line change
@@ -1,12 +1,10 @@
package ibe

import (
"bytes"
"crypto/rand"
"errors"
"fmt"

"golang.org/x/crypto/blake2s"

"github.com/drand/kyber"
"github.com/drand/kyber/pairing"
)
Expand Down Expand Up @@ -71,14 +69,14 @@ func Encrypt(s pairing.Suite, master kyber.Point, ID, msg []byte) (*Ciphertext,

// 5. Compute V = sigma XOR H2(rGid)
rGid := Gid.Mul(r, Gid) // even in Gt, it's additive notation
hrGid, err := gtToHash(rGid, len(msg), H2Tag())
hrGid, err := gtToHash(s, rGid, len(msg), H2Tag())
if err != nil {
return nil, err
}
V := xor(sigma, hrGid)

// 6. Compute M XOR H(sigma)
hsigma, err := h4(sigma, len(msg))
hsigma, err := h4(s, sigma, len(msg))
if err != nil {
return nil, err
}
Expand All @@ -94,7 +92,7 @@ func Encrypt(s pairing.Suite, master kyber.Point, ID, msg []byte) (*Ciphertext,
func Decrypt(s pairing.Suite, private kyber.Point, c *Ciphertext) ([]byte, error) {
// 1. Compute sigma = V XOR H2(e(rP,private))
gidt := s.Pair(c.U, private)
hgidt, err := gtToHash(gidt, len(c.W), H2Tag())
hgidt, err := gtToHash(s, gidt, len(c.W), H2Tag())
if err != nil {
return nil, err
}
Expand All @@ -104,7 +102,7 @@ func Decrypt(s pairing.Suite, private kyber.Point, c *Ciphertext) ([]byte, error
sigma := xor(hgidt, c.V)

// 2. Compute M = W XOR H4(sigma)
hsigma, err := h4(sigma, len(c.W))
hsigma, err := h4(s, sigma, len(c.W))
if err != nil {
return nil, err
}
Expand All @@ -124,14 +122,11 @@ func Decrypt(s pairing.Suite, private kyber.Point, c *Ciphertext) ([]byte, error

}

const maxSize = 1 << 10

// hash sigma and msg to get r
func h3(s pairing.Suite, sigma, msg []byte) (kyber.Scalar, error) {
h3, err := blake2s.NewXOF(maxSize, nil)
if err != nil {
panic(err)
}
h3 := s.Hash()
h3.Reset()
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if _, err := h3.Write(H3Tag()); err != nil {
return nil, fmt.Errorf("err hashing h3 tag: %v", err)
}
Expand All @@ -143,38 +138,46 @@ func h3(s pairing.Suite, sigma, msg []byte) (kyber.Scalar, error) {
if !ok {
panic("scalar can't be created from hash")
}
return hashable.Hash(s, h3)

h3Reader := bytes.NewReader(h3.Sum(make([]byte, h3.Size())))
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return hashable.Hash(s, h3Reader)
}

func h4(sigma []byte, length int) ([]byte, error) {
h4, err := blake2s.NewXOF(maxSize, nil)
if err != nil {
panic(err)
}
func h4(s pairing.Suite, sigma []byte, length int) ([]byte, error) {
h4 := s.Hash()
h4.Reset()
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if _, err := h4.Write(H4Tag()); err != nil {
return nil, fmt.Errorf("err writing h4tag: %v", err)
}
if _, err := h4.Write(sigma); err != nil {
return nil, fmt.Errorf("err writing sigma to h4: %v", err)
}

h4Reader := bytes.NewReader(h4.Sum(make([]byte, h4.Size())))
h4sigma := make([]byte, length)
if _, err := h4.Read(h4sigma); err != nil {

if _, err := h4Reader.Read(h4sigma); err != nil {
return nil, fmt.Errorf("err reading from h4: %v", err)
}
return h4sigma, nil
}

func gtToHash(gt kyber.Point, length int, dst []byte) ([]byte, error) {
xof, err := blake2s.NewXOF(maxSize, nil)
if err != nil {
return nil, err
}
if _, err := xof.Write(dst); err != nil {
func gtToHash(s pairing.Suite, gt kyber.Point, length int, dst []byte) ([]byte, error) {
hash := s.Hash()
hash.Reset()
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if _, err := hash.Write(dst); err != nil {
return nil, errors.New("err writing dst to gtHash")
}
gt.MarshalTo(xof)
if _, err := gt.MarshalTo(hash); err != nil {
return nil, errors.New("err marshalling gt to the hash function")
}

hashReader := bytes.NewReader(hash.Sum(make([]byte, hash.Size())))
var b = make([]byte, length)
if _, err := xof.Read(b); err != nil {
if _, err := hashReader.Read(b); err != nil {
return nil, errors.New("couldn't read from xof")
}
return b[:], nil
Expand Down