added the crypto crate with tests and function

crates/crypto/src/lib.rs

@@ -0,0 +1,56 @@
+use chacha20poly1305::{
+    ChaCha20Poly1305, Key, Nonce,
+    aead::{Aead, Generate, KeyInit},
+};
+
+type Result<T> = std::result::Result<T, Box<dyn std::error::Error>>;
+
+mod helper {
+    use super::{Generate, Key, Nonce};
+    pub fn gen_nonce() -> Nonce {
+        Nonce::generate()
+    }
+
+    pub fn gen_key() -> Key {
+        Key::generate()
+    }
+}
+
+pub fn encrypt(key: &Key, plaintext: Vec<u8>) -> Result<(Nonce, Vec<u8>)> {
+    let cipher = ChaCha20Poly1305::new(key);
+
+    let nonce = helper::gen_nonce();
+
+    let ciphertext = cipher.encrypt(&nonce, plaintext.as_ref())?;
+
+    Ok((nonce, ciphertext))
+}
+
+pub fn decrypt(key: &Key, ciphertext: Vec<u8>, nonce: &Nonce) -> Result<Vec<u8>> {
+    let cipher = ChaCha20Poly1305::new(key);
+
+    let plaintext = cipher.decrypt(nonce, ciphertext.as_ref())?;
+
+    Ok(plaintext)
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::result::Result;
+
+    #[test]
+    fn encryption_decryption() -> Result<(), Box<dyn std::error::Error>> {
+        let key = helper::gen_key();
+        let plaintext = "I alone am the honored one.\n - Saturo Gojo.";
+
+        let (nonce, ciphertext) = encrypt(&key, plaintext.into())?;
+
+        let transformed = decrypt(&key, ciphertext, &nonce)?;
+
+        assert_eq!(plaintext.as_bytes(), transformed);
+
+        Ok(())
+    }
+}
+