diff --git a/src/kasa_crypt/_crypt_impl.pyx b/src/kasa_crypt/_crypt_impl.pyx
index 3d97b7b..0a77447 100644
--- a/src/kasa_crypt/_crypt_impl.pyx
+++ b/src/kasa_crypt/_crypt_impl.pyx
@@ -22,8 +22,8 @@ cdef char* _encrypt(const char *unencrypted):
     return encrypted
 
 def encrypt(string: str) -> bytes:
-    return _encrypt(string.encode('ascii'))
+    return _encrypt(string.encode('utf-8'))
 
 
 def decrypt(string: bytes) -> str:
-    return _decrypt(string).decode('ascii')
+    return _decrypt(string).decode('utf-8')
diff --git a/src/kasa_crypt/crypt_wrapper.h b/src/kasa_crypt/crypt_wrapper.h
index 56b4872..afdb0cc 100644
--- a/src/kasa_crypt/crypt_wrapper.h
+++ b/src/kasa_crypt/crypt_wrapper.h
@@ -8,7 +8,7 @@
 void _encrypt_into(const char * unencrypted, char * encrypted) {
     uint8_t unencrypted_byte;
     uint8_t key = 171;
-    for(unsigned i = 0; i < strlen(unencrypted); i++) {
+    for(unsigned i = 0; i <= strlen(unencrypted); i++) {
         unencrypted_byte = unencrypted[i];
         key = key ^ unencrypted_byte;
         encrypted[i] = key;
@@ -18,7 +18,7 @@ void _decrypt_into(const char * encrypted, char * unencrypted) {
     uint8_t unencrypted_byte;
     uint8_t encrypted_byte;
     uint8_t key = 171;
-    for(unsigned i = 0; i < strlen(encrypted); i++) {
+    for(unsigned i = 0; i <= strlen(encrypted); i++) {
         encrypted_byte = encrypted[i];
         unencrypted_byte = key ^ encrypted_byte;
         key = encrypted_byte;