diff --git a/src/decryptor.rs b/src/decryptor.rs
index d5ef603..0271221 100644
--- a/src/decryptor.rs
+++ b/src/decryptor.rs
@@ -17,11 +17,11 @@ pub struct Aes128GcmStreamDecryptor {
 }
 
 impl Aes128GcmStreamDecryptor {
-    pub fn new(key: [u8; 16]) -> Self {
+    pub fn new(key: [u8; 16], nonce: &[u8]) -> Self {
         let key = GenericArray::from(key);
         let aes = Aes128::new(&key);
 
-        Self {
+        let mut s = Self {
             crypto: aes,
             message_buffer: vec![],
             integrality_buffer: vec![],
@@ -31,14 +31,12 @@ impl Aes128GcmStreamDecryptor {
             encryption_nonce: 0,
             adata_len: 0,
             message_len: 0,
-        }
-    }
-
-    pub fn init_nonce(&mut self, nonce: &[u8]) {
-        let (ghash_key, normalized_nonce) = self.normalize_nonce(nonce);
-        self.ghash_key = ghash_key;
-        self.init_nonce = normalized_nonce;
-        self.encryption_nonce = normalized_nonce;
+        };
+        let (ghash_key, normalized_nonce) = s.normalize_nonce(nonce);
+        s.ghash_key = ghash_key;
+        s.init_nonce = normalized_nonce;
+        s.encryption_nonce = normalized_nonce;
+        s
     }
 
     pub fn init_adata(&mut self, adata: &[u8]) {
@@ -78,7 +76,7 @@ impl Aes128GcmStreamDecryptor {
     }
 
     pub fn finalize(&mut self) -> Result<Vec<u8>, String> {
-        let mut plaintext_message = vec![];
+        let mut plaintext_message = Vec::with_capacity(16);
         let message_buffer_len = self.message_buffer.len();
         if message_buffer_len > 16 {
             // last block and this block len is less than 128 bits
diff --git a/src/encryptor.rs b/src/encryptor.rs
index 5d1a1cd..355ed43 100644
--- a/src/encryptor.rs
+++ b/src/encryptor.rs
@@ -17,11 +17,11 @@ pub struct Aes128GcmStreamEncryptor {
 }
 
 impl Aes128GcmStreamEncryptor {
-    pub fn new(key: [u8; 16]) -> Self {
+    pub fn new(key: [u8; 16], nonce: &[u8]) -> Self {
         let key = GenericArray::from(key);
         let aes = Aes128::new(&key);
 
-        Self {
+        let mut s = Self {
             crypto: aes,
             message_buffer: vec![],
             integrality_buffer: vec![],
@@ -31,14 +31,12 @@ impl Aes128GcmStreamEncryptor {
             encryption_nonce: 0,
             adata_len: 0,
             message_len: 0,
-        }
-    }
-
-    pub fn init_nonce(&mut self, nonce: &[u8]) {
-        let (ghash_key, normalized_nonce) = self.normalize_nonce(nonce);
-        self.ghash_key = ghash_key;
-        self.init_nonce = normalized_nonce;
-        self.encryption_nonce = normalized_nonce;
+        };
+        let (ghash_key, normalized_nonce) = s.normalize_nonce(nonce);
+        s.ghash_key = ghash_key;
+        s.init_nonce = normalized_nonce;
+        s.encryption_nonce = normalized_nonce;
+        s
     }
 
     pub fn init_adata(&mut self, adata: &[u8]) {
@@ -78,7 +76,7 @@ impl Aes128GcmStreamEncryptor {
     }
 
     pub fn finalize(&mut self) -> (Vec<u8>, Vec<u8>) {
-        let mut encrypted_message = vec![];
+        let mut encrypted_message = Vec::with_capacity(16);
         if !self.message_buffer.is_empty() {
             // last block and this block len is less than 128 bits
             self.encryption_nonce = inc_32(self.encryption_nonce);
diff --git a/src/main.rs b/src/main.rs
index 051fa14..81413f0 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -42,8 +42,7 @@ fn main() {
     cipher.encrypt_in_place(&nonce, &[], &mut ciphertext).unwrap();
     println!("{}", hex::encode(ciphertext.as_slice()));
 
-    let mut aes128_gcm_stream_encryptor = Aes128GcmStreamEncryptor::new([0; 16]);
-    aes128_gcm_stream_encryptor.init_nonce(&[0u8; 12]);
+    let mut aes128_gcm_stream_encryptor = Aes128GcmStreamEncryptor::new([0; 16], &[0u8; 12]);
     aes128_gcm_stream_encryptor.init_adata(&[]);
     let o1 = aes128_gcm_stream_encryptor.next(&plaintext[0..21]);
     let o2 = aes128_gcm_stream_encryptor.next(&plaintext[21..64]);
@@ -55,8 +54,7 @@ fn main() {
     println!("{}: E4", hex::encode(&o4));
     println!("{} : TAG", hex::encode(&t));
 
-    let mut aes128_gcm_stream_decryptor = Aes128GcmStreamDecryptor::new([0; 16]);
-    aes128_gcm_stream_decryptor.init_nonce(&[0u8; 12]);
+    let mut aes128_gcm_stream_decryptor = Aes128GcmStreamDecryptor::new([0; 16], &[0u8; 12]);
     let o1 = aes128_gcm_stream_decryptor.next(&hex::decode("0388dace60b6a392f328c2b971b2fe78f795aaab494b5923f7fd89ff948bc1e0200211214e7394da2089b6acd093abe0c94da219118e297d7b7ebcbcc9c388f28ade7d85a8c992f32a52151e1c2adceb7c6138e042").unwrap());
     let o2_result = aes128_gcm_stream_decryptor.finalize();
     println!("{}", hex::encode(&o1));