diff --git a/rust/ares_crypto/src/aes_siv.rs b/rust/ares_crypto/src/aes_siv.rs
index ae0559c..1d3afa9 100644
--- a/rust/ares_crypto/src/aes_siv.rs
+++ b/rust/ares_crypto/src/aes_siv.rs
@@ -1,33 +1,162 @@
-use aes_siv::aead::Error;
+use aes_siv::{
+    aead::{generic_array::GenericArray, heapless::Vec, AeadInPlace, Buffer, KeyInit},
+    Aes256SivAead,
+    Error, // Or `Aes256SivAead`
+    Nonce, siv::KeySize,
+};
 
-pub fn _ac_aes_siv_en() -> Result<(), Error> {
+pub fn _ac_aes_siv_en(
+    key: &mut [u8],
+    message: &mut [u8],
+    data: &mut [&mut [u8]],
+    iv: &[u8; 16],
+    out: &mut [u8],
+) -> Result<(), Error> {
+    eprintln!("START 0");
+    let cipher = Aes256SivAead::new_from_slice(key).unwrap();
+    eprintln!("START 1");
+    let nonce = Nonce::from_slice(b"");
+    eprintln!("START 2");
+    let mut buffer = Vec::<u8, 1024>::new();
+    eprintln!("START 3");
+    buffer.extend_from_slice(message).unwrap();
+    eprintln!("START 4");
+    let mut ad: Vec<u8, 1024> = Vec::new();
+    eprintln!("START 5");
+    for i in 0..data.len() {
+        for j in 0..data[i].len() {
+            ad.push(data[i][j]).unwrap();
+        }
+    }
+    eprintln!("ad: {:?}", ad);
+    let ad_bytes = ad.as_slice();
+    cipher.encrypt_in_place(nonce, ad_bytes, &mut buffer)?;
+    out.copy_from_slice(&buffer);
+    Ok(())
+}
+
+pub fn _ac_aes_siv_de(
+    key: &mut [u8],
+    message: &mut [u8],
+    data: &mut [&mut [u8]],
+    iv: &[u8; 16],
+    out: &mut [u8],
+) {
     todo!();
 }
 
-pub fn _ac_aes_siv_de() -> Result<(), Error> {
+pub fn ac_aes_siva_en(
+    key: &mut [u8; 32],
+    message: &mut [u8],
+    data: &mut [&mut [u8]],
+    iv: &[u8; 16],
+    out: &mut [u8],
+) {
+    _ac_aes_siv_en(key, message, data, iv, out);
+}
+
+pub fn ac_aes_siva_de(
+    key: &mut [u8; 32],
+    message: &mut [u8],
+    data: &mut [&mut [u8]],
+    iv: &[u8; 16],
+    out: &mut [u8],
+) {
     todo!();
 }
 
-pub fn ac_aes_siva_en() -> Result<(), Error> {
+pub fn ac_aes_sivb_en(
+    key: &mut [u8; 48],
+    message: &mut [u8],
+    data: &mut [&mut [u8]],
+    iv: &[u8; 16],
+    out: &mut [u8],
+) {
+    _ac_aes_siv_en(key, message, data, iv, out);
+}
+
+pub fn ac_aes_sivb_de(
+    key: &mut [u8; 48],
+    message: &mut [u8],
+    data: &mut [&mut [u8]],
+    iv: &[u8; 16],
+    out: &mut [u8],
+) {
     todo!();
 }
 
-pub fn ac_aes_siva_de() -> Result<(), Error> {
-    todo!();
+pub fn ac_aes_sivc_en(
+    key: &mut [u8; 64],
+    message: &mut [u8],
+    data: &mut [&mut [u8]],
+    iv: &[u8; 16],
+    out: &mut [u8],
+) {
+    _ac_aes_siv_en(key, message, data, iv, out);
 }
 
-pub fn ac_aes_sivb_en() -> Result<(), Error> {
-    todo!();
+pub fn ac_aes_sivc_de(
+    key: &mut [u8; 64],
+    message: &mut [u8],
+    data: &mut [&mut [u8]],
+    iv: &[u8; 16],
+    out: &mut [u8],
+) {
 }
 
-pub fn ac_aes_sivb_de() -> Result<(), Error> {
-    todo!();
-}
+#[cfg(test)]
+#[cfg(feature = "test_vs_urcrypt")]
+mod urcrypt_tests {
+    use super::{
+        ac_aes_siva_de, ac_aes_siva_en, ac_aes_sivb_de, ac_aes_sivb_en, ac_aes_sivc_de,
+        ac_aes_sivc_en,
+    };
+    use urcrypt_sys::{
+        urcrypt_aes_siv_data, urcrypt_aes_siva_de, urcrypt_aes_siva_en, urcrypt_aes_sivb_de,
+        urcrypt_aes_sivb_en, urcrypt_aes_sivc_de, urcrypt_aes_sivc_en,
+    };
 
-pub fn ac_aes_sivc_en() -> Result<(), Error> {
-    todo!();
-}
+    #[test]
+    fn test_aes_siva_en() {
+        let mut key: [u8; 32] = [42; 32];
+        let mut message: [u8; 32] = [42; 32];
+        let mut iv: [u8; 16] = [42; 16];
+        let mut uc_out: [u8; 32] = [0; 32];
 
-pub fn ac_aes_sivc_de() -> Result<(), Error> {
-    todo!();
+        let mut uc_bytes = [42; 32];
+        let mut uc_bytes_two = [43; 32];
+        let mut uc_data: [urcrypt_aes_siv_data; 2] = [
+            urcrypt_aes_siv_data {
+                bytes: uc_bytes.as_mut_ptr(),
+                length: uc_bytes.len(),
+            },
+            urcrypt_aes_siv_data {
+                bytes: uc_bytes_two.as_mut_ptr(),
+                length: uc_bytes_two.len(),
+            },
+        ];
+
+        unsafe {
+            urcrypt_aes_siva_en(
+                message.as_mut_ptr(),
+                message.len(),
+                uc_data.as_mut_ptr(),
+                uc_data.len(),
+                key.as_mut_ptr(),
+                iv.as_mut_ptr(),
+                uc_out.as_mut_ptr(),
+            )
+        };
+        eprintln!("uc_out: {:?}", uc_out);
+
+        let mut key: [u8; 32] = [42; 32];
+        let mut message: [u8; 32] = [42; 32];
+        let mut ac_data: [&mut [u8]; 2] = [&mut [42; 32], &mut [43; 32]];
+        let iv: [u8; 16] = [42; 16];
+        let mut ac_out: [u8; 32] = [0; 32];
+        ac_aes_siva_en(&mut key, &mut message, &mut ac_data, &iv, &mut ac_out);
+        eprintln!("ac_out: {:?}", ac_out);
+
+        assert_eq!(ac_out, uc_out);
+    }
 }