diff --git a/core/auth.js b/core/auth.js
index 5aa61d3d..49fcfa13 100644
--- a/core/auth.js
+++ b/core/auth.js
@@ -45,12 +45,12 @@ function readSession(session) {
 	let jwt_parts = session?.split('.');
 	if (jwt_parts?.length === 3) {
 		let [header, payload, signature] = jwt_parts;
-		header = JSON.parse(base64Decode(unb64url(header)));
+		header = JSON.parse(utf8Decode(base64Decode(unb64url(header))));
 		if (header.typ === 'JWT' && header.alg === 'HS256') {
 			signature = unb64url(signature);
 			let id = ssb.getIdentities(':auth');
 			if (id?.length && ssb.hmacsha256verify(id[0], payload, signature)) {
-				let result = JSON.parse(base64Decode(unb64url(payload)));
+				let result = JSON.parse(utf8Decode(base64Decode(unb64url(payload))));
 				let now = new Date().valueOf()
 				if (now < result.exp) {
 					print(`JWT valid for another ${(result.exp - now) / 1000} seconds.`);
diff --git a/src/tests.c b/src/tests.c
index f485476d..bc9e4063 100644
--- a/src/tests.c
+++ b/src/tests.c
@@ -653,7 +653,7 @@ static void _test_b64(const tf_test_options_t* options)
 	fprintf(file,
 		"'use strict';\n"
 		"print(base64Encode('hello'));\n"
-		"let x = base64Decode(base64Encode('hello'));\n"
+		"let x = utf8Decode(base64Decode(base64Encode('hello')));\n"
 		"if (x !== 'hello') {\n"
 		"	print(x);\n"
 		"	exit(1);\n"
diff --git a/src/util.js.c b/src/util.js.c
index ec749163..607d35d9 100644
--- a/src/util.js.c
+++ b/src/util.js.c
@@ -1,5 +1,6 @@
 #include "util.js.h"
 
+#include "bip39.h"
 #include "log.h"
 #include "mem.h"
 #include "task.h"
@@ -71,8 +72,20 @@ JSValue tf_util_utf8_decode(JSContext* context, JSValue value)
 static JSValue _util_base64_encode(JSContext* context, JSValueConst this_val, int argc, JSValueConst* argv)
 {
 	JSValue result = JS_UNDEFINED;
+	JSValue buffer = JS_UNDEFINED;
 	size_t length = 0;
 	uint8_t* array = tf_util_try_get_array_buffer(context, &length, argv[0]);
+	if (!array)
+	{
+		size_t offset;
+		size_t element_size;
+		buffer = tf_util_try_get_typed_array_buffer(context, argv[0], &offset, &length, &element_size);
+		if (!JS_IsException(buffer))
+		{
+			array = tf_util_try_get_array_buffer(context, &length, buffer);
+		}
+	}
+
 	if (array)
 	{
 		char* encoded = tf_malloc(length * 4);
@@ -95,6 +108,7 @@ static JSValue _util_base64_encode(JSContext* context, JSValueConst this_val, in
 		tf_free(encoded);
 		JS_FreeCString(context, value);
 	}
+	JS_FreeValue(context, buffer);
 	return result;
 }
 
@@ -103,19 +117,58 @@ static JSValue _util_base64_decode(JSContext* context, JSValueConst this_val, in
 	JSValue result = JS_UNDEFINED;
 	size_t length = 0;
 	const char* value = JS_ToCStringLen(context, &length, argv[0]);
-	uint8_t* encoded = tf_malloc(length);
+	uint8_t* decoded = tf_malloc(length);
 
-	int r = tf_base64_decode(value, length, encoded, length);
+	int r = tf_base64_decode(value, length, decoded, length);
 	if (r >= 0)
 	{
-		result = JS_NewStringLen(context, (const char*)encoded, r);
+		result = tf_util_new_uint8_array(context, decoded, r);
 	}
 
-	tf_free(encoded);
+	tf_free(decoded);
 	JS_FreeCString(context, value);
 	return result;
 }
 
+static JSValue _util_bip39_words(JSContext* context, JSValueConst this_val, int argc, JSValueConst* argv)
+{
+	JSValue result = JS_UNDEFINED;
+	JSValue buffer = JS_UNDEFINED;
+	size_t length;
+	uint8_t* array = tf_util_try_get_array_buffer(context, &length, argv[0]);
+	if (!array)
+	{
+		size_t offset;
+		size_t element_size;
+		buffer = tf_util_try_get_typed_array_buffer(context, argv[0], &offset, &length, &element_size);
+		if (!JS_IsException(buffer))
+		{
+			array = tf_util_try_get_array_buffer(context, &length, buffer);
+		}
+	}
+
+	char words[2048] = "";
+	if (array && tf_bip39_bytes_to_words(array, length, words, sizeof(words)))
+	{
+		result = JS_NewString(context, words);
+	}
+	JS_FreeValue(context, buffer);
+	return result;
+}
+
+static JSValue _util_bip39_bytes(JSContext* context, JSValueConst this_val, int argc, JSValueConst* argv)
+{
+	const char* words = JS_ToCString(context, argv[0]);
+	uint8_t bytes[33] = { 0 };
+	bool success = tf_bip39_words_to_bytes(words, bytes, sizeof(bytes));
+	JS_FreeCString(context, words);
+	if (success)
+	{
+		return tf_util_new_uint8_array(context, bytes, sizeof(bytes));
+	}
+	return JS_UNDEFINED;
+}
+
 uint8_t* tf_util_try_get_array_buffer(JSContext* context, size_t* psize, JSValueConst obj)
 {
 	uint8_t* result = JS_GetArrayBuffer(context, psize, obj);
@@ -434,6 +487,8 @@ void tf_util_register(JSContext* context)
 	JS_SetPropertyStr(context, global, "utf8Encode", JS_NewCFunction(context, _util_utf8_encode, "utf8Encode", 1));
 	JS_SetPropertyStr(context, global, "base64Decode", JS_NewCFunction(context, _util_base64_decode, "base64Decode", 1));
 	JS_SetPropertyStr(context, global, "base64Encode", JS_NewCFunction(context, _util_base64_encode, "base64Encode", 1));
+	JS_SetPropertyStr(context, global, "bip39Words", JS_NewCFunction(context, _util_bip39_words, "bip39Words", 1));
+	JS_SetPropertyStr(context, global, "bip39Bytes", JS_NewCFunction(context, _util_bip39_bytes, "bip39Bytes", 1));
 	JS_SetPropertyStr(context, global, "print", JS_NewCFunction(context, _util_print, "print", 1));
 	JS_SetPropertyStr(context, global, "setTimeout", JS_NewCFunction(context, _util_setTimeout, "setTimeout", 2));
 	JS_SetPropertyStr(context, global, "parseHttpRequest", JS_NewCFunction(context, _util_parseHttpRequest, "parseHttpRequest", 2));