specify mix key to be used and mount mix

Author: chaitanyaprem

waku/factory/external_config.nim

@@ -663,6 +663,16 @@ with the drawback of consuming some more bandwidth.""",
       name: "rendezvous"
     .}: bool
 
+    #Mix config
+    mixkey* {.desc: "ED25519 private key as 64 char hex string.", name: "mixkey".}:
+      Option[string]
+    #TODO: Temp config for simulations.Ideally need to get this info from bootstrap ENRs
+#[     mixBootstrapNodes* {. 
+      desc:
+        "Text-encoded data for mix bootstrap node. Encoded in the format Multiaddress:libp2pPubKey:MixPubKey. Argument may be repeated.",
+      name: "mix-bootstrap-node"
+    .}: seq[string] ]#
+
     ## websocket config
     websocketSupport* {.
       desc: "Enable websocket:  true|false",

waku/factory/node_factory.nim

@@ -422,6 +422,17 @@ proc setupProtocols(
       return
         err("failed to set node waku peer-exchange peer: " & peerExchangeNode.error)
 
+  #mount mix
+  let mixPrivKey:string =
+    if conf.mixkey.isSome():
+      conf.mixkey.get()
+    else:
+      error "missing mix key"
+      return err("missing mix key")
+  (
+    await node.mountMix(mixPrivKey)
+  ).isOkOr:
+    return err("failed to mount waku mix protocol: " & $error)
   return ok()
 
 ## Start node

waku/node/waku_node.nim

@@ -12,6 +12,7 @@ import
   bearssl/rand,
   eth/p2p/discoveryv5/enr,
   libp2p/crypto/crypto,
+  libp2p/crypto/curve25519,
   libp2p/protocols/ping,
   libp2p/protocols/pubsub/gossipsub,
   libp2p/protocols/pubsub/rpc/messages,
@@ -126,6 +127,7 @@ type
     contentTopicHandlers: Table[ContentTopic, TopicHandler]
     rateLimitSettings*: ProtocolRateLimitSettings
     mix*: MixProtocol
+    mixbootNodes*: Table[PeerId, MixPubInfo]
 
 proc new*(
     T: type WakuNode,
@@ -212,24 +214,20 @@ proc mountSharding*(
   return ok()
 
  # Mix Protocol
-proc mountMix*(node: WakuNode): Result[void, string] =
+proc mountMix*(node: WakuNode, mixPrivKey: string): Future[Result[void, string]] {.async.}  =
   info "mounting mix protocol" #TODO log the config used
-
-  var mixNodes = initTable[PeerId, MixPubInfo]()
-  # TODO: pass bootstrap node info here as mixNodes
-
-  let keyPairResult = generateKeyPair()
-  if keyPairResult.isErr:
-    return err("Generate key pair error: " & $keyPairResult.error)
-  let (mixPrivKey, mixPubKey) = keyPairResult.get()
+  let mixKey = nimcrypto.fromHex(mixPrivKey).intoCurve25519Key()
+  let mixPubKey = public(mixKey)
 
   let localaddrStr = node.announcedAddresses[0].toString().valueOr:
     return err("Failed to convert multiaddress to string.")
 
   let localMixNodeInfo = initMixNodeInfo(
-    localaddrStr, mixPubKey, mixPrivKey, node.switch.peerInfo.publicKey.skkey,
+    localaddrStr, mixPubKey, mixKey, node.switch.peerInfo.publicKey.skkey,
     node.switch.peerInfo.privateKey.skkey,
   )
+  let mixNodes = initTable[PeerId, MixPubInfo]()
+  #mixNodes[""]= 
 
   let protoRes = MixProtocol.initMix(localMixNodeInfo, node.switch, mixNodes)
   if protoRes.isErr: