allow storing private keys in the vault

web/polyfills.buffer.ts

@@ -206,3 +206,31 @@ function utf8ToBytes (string, units) {
     }
     return bytes
 }
+
+// Create lookup table for `toString('hex')`
+// See: https://github.com/feross/buffer/issues/219
+const hexSliceLookupTable = (function () {
+    const alphabet = '0123456789abcdef'
+    const table = new Array(256)
+    for (let i = 0; i < 16; ++i) {
+        const i16 = i * 16
+        for (let j = 0; j < 16; ++j) {
+            table[i16 + j] = alphabet[i] + alphabet[j]
+        }
+    }
+    return table
+})()
+
+
+export function hexSlice (start, end) {
+    const len = this.length
+
+    if (!start || start < 0) {start = 0}
+    if (!end || end < 0 || end > len) {end = len}
+
+    let out = ''
+    for (let i = start; i < end; ++i) {
+        out += hexSliceLookupTable[this[i]]
+    }
+    return out
+}