From 7a46cf371e31b6020a3dbaa240e752e78b212495 Mon Sep 17 00:00:00 2001
From: "Richard T. Carback III" <rick.carback@gmail.com>
Date: Thu, 2 Dec 2021 02:08:07 +0000
Subject: [PATCH] Add function to generate session keys with DH and SIDH keys
---
storage/e2e/key.go | 37 ++++++++++++++++++++++++++++++++++++-
1 file changed, 36 insertions(+), 1 deletion(-)
diff --git a/storage/e2e/key.go b/storage/e2e/key.go
index 49900a09a..ed40e54e5 100644
--- a/storage/e2e/key.go
+++ b/storage/e2e/key.go
@@ -12,8 +12,42 @@ import (
e2eCrypto "gitlab.com/elixxir/crypto/e2e"
"gitlab.com/elixxir/crypto/hash"
"gitlab.com/elixxir/primitives/format"
+ "github.com/cloudflare/circl/dh/sidh"
+ "gitlab.com/elixxir/crypto/cyclic"
+ dh "gitlab.com/elixxir/crypto/diffieHellman"
+ jww "github.com/spf13/jwalterweatherman"
)
+// GenerateE2ESessionBaseKey returns the baseKey symmetric encryption key root.
+// The baseKey is created by hashing the results of the diffie-helman (DH) key
+// exchange with the post-quantum secure Supersingular Isogeny DH exchange
+// results.
+func GenerateE2ESessionBaseKey(myDHPrivKey, theirDHPubKey *cyclic.Int,
+ dhGrp *cyclic.Group, mySIDHPrivKey *sidh.PrivateKey,
+ theirSIDHPubKey *sidh.PublicKey) *cyclic.Int {
+ // DH Key Gen
+ dhKey := dh.GenerateSessionKey(myDHPrivKey, theirDHPubKey, dhGrp)
+
+ // SIDH Key Gen
+ sidhKey := make([]byte, mySIDHPrivKey.SharedSecretSize())
+ mySIDHPrivKey.DeriveSecret(sidhKey, theirSIDHPubKey)
+
+ // Derive key
+ h := hash.CMixHash.New()
+ h.Write(dhKey.Bytes())
+ h.Write(sidhKey)
+ keyDigest := h.Sum(nil)
+ // NOTE: Sadly the baseKey was a full DH key, and that key was used
+ // to create an "IDF" as well as in key generation and potentially other
+ // downstream code. We use a KDF to limit scope of the change,'
+ // generating into the same group as DH to preserve any kind of
+ // downstream reliance on the size of the key for now.
+ baseKey := hash.ExpandKey(hash.CMixHash.New, dhGrp, keyDigest,
+ dhGrp.NewInt(1))
+
+ return baseKey
+}
+
type Key struct {
// Links
session *Session
@@ -96,7 +130,8 @@ func (k *Key) denoteUse() {
k.session.useKey(k.keyNum)
}
-// Generates the key and returns it
+// generateKey derives the current e2e key from the baseKey and the index
+// keyNum and returns it
func (k *Key) generateKey() e2eCrypto.Key {
return e2eCrypto.DeriveKey(k.session.baseKey, k.keyNum,
k.session.relationshipFingerprint)
--
GitLab