feat(aes-cbc): embed IV in encrypted output

aes/src/cbc.rs

@@ -44,13 +44,19 @@ impl AesCbc {
 
     /// Encrypts plaintext using CBC mode with PKCS#7 padding.
     ///
+    /// The output format is: `[16-byte IV][ciphertext...]`
+    ///
     /// # Errors
     ///
     /// Returns `CipherError` if encryption fails.
     #[allow(clippy::missing_panics_doc)]
     pub fn encrypt(&self, plaintext: &[u8]) -> CipherResult<Vec<u8>> {
         let padded = pkcs7_pad(plaintext, BLOCK_SIZE);
-        let mut ciphertext = Vec::with_capacity(padded.len());
+        let mut output = Vec::with_capacity(BLOCK_SIZE + padded.len());
+
+        // Prepend IV to output
+        output.extend_from_slice(&self.iv.to_be_bytes());
+
         let mut prev_block = self.iv.to_block();
 
         for chunk in padded.chunks_exact(BLOCK_SIZE) {
@@ -58,30 +64,36 @@ impl AesCbc {
             let plain_block = Block128::from_be_bytes(chunk.try_into().expect("exact chunk size"));
             let xored = plain_block ^ prev_block.as_u128();
             let encrypted = self.aes.encrypt_block(xored);
-            ciphertext.extend_from_slice(&encrypted.to_be_bytes());
+            output.extend_from_slice(&encrypted.to_be_bytes());
             prev_block = encrypted;
         }
 
-        Ok(ciphertext)
+        Ok(output)
     }
 
     /// Decrypts ciphertext using CBC mode and removes PKCS#7 padding.
     ///
+    /// Expects input format: `[16-byte IV][ciphertext...]`
+    /// The IV is extracted from the input; the IV stored in `self` is ignored.
+    ///
     /// # Errors
     ///
-    /// Returns `CipherError::InvalidBlockSize` if ciphertext length is not a multiple of 16.
+    /// Returns `CipherError::InvalidBlockSize` if input length is not a multiple of 16
+    /// or is less than 32 bytes (IV + at least one block).
     /// Returns `CipherError::InvalidPadding` if padding is invalid.
     #[allow(clippy::missing_panics_doc)]
-    pub fn decrypt(&self, ciphertext: &[u8]) -> CipherResult<Vec<u8>> {
-        if ciphertext.is_empty() || !ciphertext.len().is_multiple_of(BLOCK_SIZE) {
-            return Err(CipherError::invalid_block_size(
-                BLOCK_SIZE,
-                ciphertext.len(),
-            ));
+    pub fn decrypt(&self, data: &[u8]) -> CipherResult<Vec<u8>> {
+        // Need at least IV (16 bytes) + one ciphertext block (16 bytes)
+        if data.len() < BLOCK_SIZE * 2 || !data.len().is_multiple_of(BLOCK_SIZE) {
+            return Err(CipherError::invalid_block_size(BLOCK_SIZE, data.len()));
         }
 
+        // Extract IV from first block
+        let iv = Iv::from_be_bytes(data[..BLOCK_SIZE].try_into().expect("exact IV size"));
+        let ciphertext = &data[BLOCK_SIZE..];
+
         let mut plaintext = Vec::with_capacity(ciphertext.len());
-        let mut prev_block = self.iv.to_block();
+        let mut prev_block = iv.to_block();
 
         for chunk in ciphertext.chunks_exact(BLOCK_SIZE) {
             // chunks_exact guarantees exactly BLOCK_SIZE bytes
@@ -123,8 +135,8 @@ mod tests {
 
         let plaintext = [0u8; 16];
         let ciphertext = assert_ok!(cipher.encrypt(&plaintext));
-        // Padded to 32 bytes (16 data + 16 padding)
-        assert_eq!(ciphertext.len(), 32);
+        // 16 IV + 16 data + 16 padding = 48 bytes
+        assert_eq!(ciphertext.len(), 48);
 
         let decrypted = assert_ok!(cipher.decrypt(&ciphertext));
         assert_eq!(decrypted, plaintext);

aes/tests/aes_cbc.rs

@@ -33,9 +33,10 @@ fn nist_single_block_encrypt() {
 
     let ciphertext = assert_ok!(cipher.encrypt(&plaintext));
 
-    // Result includes PKCS#7 padding (16 bytes padding for aligned input)
-    assert_eq!(ciphertext.len(), 32);
-    assert_eq!(&ciphertext[..16], &expected);
+    // 16 IV + 16 block + 16 padding = 48 bytes
+    assert_eq!(ciphertext.len(), 48);
+    // First 16 bytes are IV, next 16 are the ciphertext
+    assert_eq!(&ciphertext[16..32], &expected);
 }
 
 #[test]
@@ -68,10 +69,10 @@ fn nist_multi_block_encrypt() {
 
     let ciphertext = assert_ok!(cipher.encrypt(&plaintext));
 
-    // Result includes padding (64 + 16 = 80 bytes)
-    assert_eq!(ciphertext.len(), 80);
-    // First 3 blocks should match NIST vectors exactly
-    assert_eq!(&ciphertext[..48], &expected[..48]);
+    // 16 IV + 64 blocks + 16 padding = 96 bytes
+    assert_eq!(ciphertext.len(), 96);
+    // First 16 bytes are IV, then ciphertext blocks
+    assert_eq!(&ciphertext[16..64], &expected[..48]);
 }
 
 #[test]
@@ -94,8 +95,8 @@ fn empty_plaintext() {
     let cipher = AesCbc::new(NIST_KEY, Iv::new(NIST_IV));
 
     let ciphertext = assert_ok!(cipher.encrypt(&[]));
-    // Empty input gets full block of padding
-    assert_eq!(ciphertext.len(), 16);
+    // 16 IV + 16 padding = 32 bytes
+    assert_eq!(ciphertext.len(), 32);
 
     let decrypted = assert_ok!(cipher.decrypt(&ciphertext));
     assert!(decrypted.is_empty());

cipher-factory/src/algorithm.rs

@@ -79,11 +79,15 @@ impl Algorithm {
 
     /// Decrypts data using CBC mode and removes PKCS#7 padding.
     ///
+    /// The IV is extracted from the first 16 bytes of the ciphertext.
+    ///
     /// # Errors
     ///
     /// Returns `CipherError` if decryption fails or padding is invalid.
-    pub fn decrypt_cbc(&self, key: &str, iv: &str, ciphertext: &[u8]) -> CipherResult<Vec<u8>> {
-        let cipher = self.new_cbc_cipher(key, iv)?;
+    pub fn decrypt_cbc(&self, key: &str, ciphertext: &[u8]) -> CipherResult<Vec<u8>> {
+        // IV is embedded in ciphertext, use dummy IV for cipher construction
+        let dummy_iv = "0x00000000000000000000000000000000";
+        let cipher = self.new_cbc_cipher(key, dummy_iv)?;
         cipher.decrypt(ciphertext)
     }
 

web/src/components/cipher_form_cbc.rs

@@ -47,13 +47,16 @@ pub fn CipherFormCbc() -> AnyView {
             return;
         }
 
+        // IV is only required for encryption (it's embedded in ciphertext for decryption)
+        let formatted_iv = if mode.get() == OperationMode::Encrypt {
             if iv.is_empty() {
                 set_error_msg("Please enter an initialization vector (IV).".to_string());
                 return;
             }
-
-        // Format IV with 0x prefix (key keeps user format, IV is always hex)
-        let formatted_iv = format!("0x{iv}");
+            format!("0x{iv}")
+        } else {
+            String::new()
+        };
 
         // Get input data
         let input_data = match input_mode.get() {
@@ -97,20 +100,16 @@ pub fn CipherFormCbc() -> AnyView {
                     Err(e) => set_error_msg(e.to_string()),
                 }
             }
-            OperationMode::Decrypt => {
-                match Algorithm::AesCbc.decrypt_cbc(&key, &formatted_iv, &input_data) {
+            OperationMode::Decrypt => match Algorithm::AesCbc.decrypt_cbc(&key, &input_data) {
                 Ok(plaintext) => {
                     set_output_bytes(Some(plaintext.clone()));
                     let formatted = match output_fmt.get() {
-                            OutputFormat::Text => {
-                                String::from_utf8(plaintext).unwrap_or_else(|_| {
+                        OutputFormat::Text => String::from_utf8(plaintext).unwrap_or_else(|_| {
                             set_error_msg(
-                                        "Output contains invalid UTF-8. Try Hex format."
-                                            .to_string(),
+                                "Output contains invalid UTF-8. Try Hex format.".to_string(),
                             );
                             String::new()
-                                })
-                            }
+                        }),
                         OutputFormat::Hex => bytes_to_hex(&plaintext),
                         OutputFormat::Binary => bytes_to_binary(&plaintext),
                         OutputFormat::Octal => bytes_to_octal(&plaintext),
@@ -118,8 +117,7 @@ pub fn CipherFormCbc() -> AnyView {
                     set_output(formatted);
                 }
                 Err(e) => set_error_msg(e.to_string()),
-                }
-            }
+            },
         }
     };
 
@@ -164,7 +162,13 @@ pub fn CipherFormCbc() -> AnyView {
                 update_output=update_output
             />
             <KeyInput key_input=key_input set_key_input=set_key_input key_size=KeySize::Aes128 />
-            <IvInput iv_input=iv_input set_iv_input=set_iv_input />
+            {move || {
+                if mode.get() == OperationMode::Encrypt {
+                    view! { <IvInput iv_input=iv_input set_iv_input=set_iv_input /> }.into_any()
+                } else {
+                    view! { <span></span> }.into_any()
+                }
+            }}
 
             <FileTextInput
                 input_mode=input_mode