[fix] Correct deprecations warnings raised into Nodejs v10

https://stackoverflow.com/questions/52165333/deprecationwarning-buffer-is-deprecated-due-to-security-and-usability-issues

app/lib/common-libs/crypto/keyring.ts

@@ -72,8 +72,8 @@ export function randomKey() {
   }
   const keypair = nacl.sign.keyPair.fromSeed(byteseed)
   return new Key(
-    Base58encode(new Buffer(keypair.publicKey)),
-    Base58encode(new Buffer(keypair.secretKey))
+    Base58encode(Buffer.from(keypair.publicKey)),
+    Base58encode(Buffer.from(keypair.secretKey))
   )
 }
 

app/lib/common-libs/crypto/nacl-util.ts

@@ -28,7 +28,7 @@ export const encodeUTF8 = function(arr:any[]) {
 
 export const encodeBase64 = function(arr:Uint8Array) {
   if (typeof btoa === 'undefined' || !window) {
-    return (new Buffer(arr)).toString('base64');
+    return (Buffer.alloc(arr)).toString('base64');
   } else {
     let i, s = [], len = arr.length;
     for (i = 0; i < len; i++) s.push(String.fromCharCode(arr[i]));
@@ -38,7 +38,7 @@ export const encodeBase64 = function(arr:Uint8Array) {
 
 export const decodeBase64 = function(s:string) {
   if (typeof atob === 'undefined' || !window) {
-    return new Uint8Array(Array.prototype.slice.call(new Buffer(s, 'base64'), 0));
+    return new Uint8Array(Array.prototype.slice.call(Buffer.from(s, 'base64'), 0));
   } else {
     let i, d = atob(s), b = new Uint8Array(d.length);
     for (i = 0; i < d.length; i++) b[i] = d.charCodeAt(i);

app/modules/keypair/lib/scrypt.ts

@@ -32,8 +32,8 @@ export const Scrypt = async (salt:string, key:string, N = 4096, r = 16, p = 1) =
   const keyBytes = await getScryptKey(key, salt, N, r, p)
   const pair = nacl.sign.keyPair.fromSeed(keyBytes);
   return {
-    pub: Base58encode(new Buffer(pair.publicKey, 'hex')),
-    sec: Base58encode(new Buffer(pair.secretKey, 'hex'))
+    pub: Base58encode(Buffer.from(pair.publicKey, 'hex')),
+    sec: Base58encode(Buffer.from(pair.secretKey, 'hex'))
   };
 }