diff --git a/background.html b/background.html
index 2fc413092..e8e85a4b4 100644
--- a/background.html
+++ b/background.html
@@ -16,7 +16,7 @@
             img-src 'self' blob: data:;
             media-src 'self' blob:;
             object-src 'none';
-            script-src 'self';
+            script-src 'self' 'unsafe-eval';
             style-src 'self' 'unsafe-inline';"
   >
   <title>Session</title>
diff --git a/ts/receiver/mediumGroups.ts b/ts/receiver/mediumGroups.ts
index 509d154de..cfec33351 100644
--- a/ts/receiver/mediumGroups.ts
+++ b/ts/receiver/mediumGroups.ts
@@ -8,19 +8,13 @@ import _ from 'lodash';
 
 import * as SenderKeyAPI from '../session/medium_group';
 import { getChainKey } from '../session/medium_group/ratchet';
-import { StringUtils } from '../session/utils';
-import { BufferType } from '../session/utils/String';
-import { ConversationModel } from '../../js/models/conversations';
+import { fromHex, toHex } from '../session/utils/String';
 import { UserUtil } from '../util';
 import {
   createSenderKeyForGroup,
-  RatchetState,
   shareSenderKeys,
 } from '../session/medium_group/senderKeys';
 
-const toHex = (d: BufferType) => StringUtils.decode(d, 'hex');
-const fromHex = (d: string) => StringUtils.encode(d, 'hex');
-
 async function handleSenderKeyRequest(
   envelope: EnvelopePlus,
   groupUpdate: SignalService.MediumGroupUpdate
diff --git a/ts/session/crypto/MessageEncrypter.ts b/ts/session/crypto/MessageEncrypter.ts
index 7e4edaa90..066ed5c0b 100644
--- a/ts/session/crypto/MessageEncrypter.ts
+++ b/ts/session/crypto/MessageEncrypter.ts
@@ -6,6 +6,8 @@ import { encryptWithSenderKey } from '../../session/medium_group/ratchet';
 import { PubKey } from '../types';
 import { StringUtils } from '../utils';
 
+import * as libsodiumwrappers from 'libsodium-wrappers';
+
 /**
  * Add padding to a message buffer
  * @param messageBuffer The buffer to add padding to.
@@ -69,6 +71,76 @@ export async function encrypt(
   return encryptUsingSealedSender(device, innerCipherText);
 }
 
+async function getSodium(): Promise<typeof libsodiumwrappers> {
+  await libsodiumwrappers.ready;
+  return libsodiumwrappers;
+}
+
+const concatUInt8Array = (...args: Array<Uint8Array>): Uint8Array => {
+  const totalLength = args.reduce((acc, current) => acc + current.length, 0);
+
+  const concatted = new Uint8Array(totalLength);
+  let currentIndex = 0;
+  args.forEach(arr => {
+    concatted.set(arr, currentIndex);
+    currentIndex += arr.length;
+  });
+
+  return concatted;
+};
+
+export async function encryptUsingSessionProtocol(
+  recipientHexEncodedX25519PublicKey: PubKey,
+  plaintext: Uint8Array
+): Promise<Uint8Array> {
+  const userED25519KeyPairHex = await UserUtil.getUserED25519KeyPair();
+  if (!userED25519KeyPairHex) {
+    throw new Error("Couldn't find user ED25519 key pair.");
+  }
+  const sodium = await getSodium();
+
+  const recipientX25519PublicKeyWithoutPrefix = PubKey.remove05PrefixIfNeeded(
+    recipientHexEncodedX25519PublicKey.key
+  );
+
+  const recipientX25519PublicKey = new Uint8Array(
+    StringUtils.fromHex(recipientX25519PublicKeyWithoutPrefix)
+  );
+  const userED25519PubKeyBytes = new Uint8Array(
+    StringUtils.fromHex(userED25519KeyPairHex.pubKey)
+  );
+  const userED25519SecretKeyBytes = new Uint8Array(
+    StringUtils.fromHex(userED25519KeyPairHex.privKey)
+  );
+
+  // merge all arrays into one
+  const data = concatUInt8Array(
+    plaintext,
+    userED25519PubKeyBytes,
+    recipientX25519PublicKey
+  );
+
+  const signature = sodium.crypto_sign(data, userED25519SecretKeyBytes);
+  if (!signature) {
+    throw new Error("Couldn't sign message");
+  }
+
+  const dataForBoxSeal = concatUInt8Array(
+    plaintext,
+    userED25519PubKeyBytes,
+    signature
+  );
+
+  const ciphertext = sodium.crypto_box_seal(
+    dataForBoxSeal,
+    recipientX25519PublicKey
+  );
+  if (!ciphertext) {
+    throw new Error("Couldn't encrypt message.");
+  }
+  return ciphertext;
+}
+
 export async function encryptForMediumGroup(
   device: PubKey,
   plainTextBuffer: Uint8Array
diff --git a/ts/session/types/PubKey.ts b/ts/session/types/PubKey.ts
index 7e63b32e9..304c7bb42 100644
--- a/ts/session/types/PubKey.ts
+++ b/ts/session/types/PubKey.ts
@@ -68,6 +68,13 @@ export class PubKey {
     return this.regex.test(pubkeyString);
   }
 
+  public static remove05PrefixIfNeeded(recipient: string): string {
+    if (recipient.length === 66 && recipient.startsWith('05')) {
+      return recipient.substr(2);
+    }
+    return recipient;
+  }
+
   public isEqual(comparator: PubKey | string) {
     return comparator instanceof PubKey
       ? this.key === comparator.key
diff --git a/ts/session/utils/String.ts b/ts/session/utils/String.ts
index 120d4e91a..8a4ea7f69 100644
--- a/ts/session/utils/String.ts
+++ b/ts/session/utils/String.ts
@@ -29,3 +29,6 @@ export function decode(buffer: BufferType, stringEncoding: Encoding): string {
 export function nonNullish<V>(v: V): v is NonNullable<V> {
   return v !== undefined && v !== null;
 }
+
+export const toHex = (d: BufferType) => decode(d, 'hex');
+export const fromHex = (d: string) => encode(d, 'hex');
diff --git a/ts/util/user.ts b/ts/util/user.ts
index 0d074af61..ec107ab3c 100644
--- a/ts/util/user.ts
+++ b/ts/util/user.ts
@@ -2,6 +2,13 @@ import { getItemById } from '../../js/modules/data';
 import { KeyPair } from '../../libtextsecure/libsignal-protocol';
 import { PrimaryPubKey } from '../session/types';
 import { MultiDeviceProtocol } from '../session/protocols';
+import { StringUtils } from '../session/utils';
+import _ from 'lodash';
+
+export type HexKeyPair = {
+  pubKey: string;
+  privKey: string;
+};
 
 export async function getCurrentDevicePubKey(): Promise<string | undefined> {
   const item = await getItemById('number_id');
@@ -17,8 +24,27 @@ export async function getPrimary(): Promise<PrimaryPubKey> {
   return MultiDeviceProtocol.getPrimaryDevice(ourNumber);
 }
 
+/**
+ * This return the stored x25519 identity keypair for that user
+ */
 export async function getIdentityKeyPair(): Promise<KeyPair | undefined> {
   const item = await getItemById('identityKey');
 
   return item?.value;
 }
+
+export async function getUserED25519KeyPair(): Promise<HexKeyPair | undefined> {
+  // 'identityKey' keeps the ed25519KeyPair under a ed25519KeyPair field.
+  // it is only set if the user migrated to the ed25519 way of generating a key
+  const item = await getItemById('identityKey');
+  const ed25519KeyPair = item?.value?.ed25519KeyPair;
+  if (ed25519KeyPair?.publicKey && ed25519KeyPair?.privateKey) {
+    const pubKeyAsArray = _.map(ed25519KeyPair.publicKey, a => a);
+    const privKeyAsArray = _.map(ed25519KeyPair.privateKey, a => a);
+    return {
+      pubKey: StringUtils.toHex(new Uint8Array(pubKeyAsArray)),
+      privKey: StringUtils.toHex(new Uint8Array(privKeyAsArray)),
+    };
+  }
+  return undefined;
+}