doc: module doc + readme

src/lib.rs

@@ -1,4 +1,5 @@
 //! _Tencent modified TEA_ (tc_tea) is a variant of the standard TEA (Tiny Encryption Algorithm).
+//!
 //! Notably, it uses a different round number and uses a "tweaked" CBC mode.
 
 mod stream_ext;

src/tc_tea.rs

@@ -8,6 +8,9 @@ const SALT_LEN: usize = 2;
 const ZERO_LEN: usize = 7;
 const FIXED_PADDING_LEN: usize = 1 + SALT_LEN + ZERO_LEN;
 
+/// Calculate expected size of encrypted data.
+///
+/// `body_size` is the size of data you'd like to encrypt.
 pub fn calc_encrypted_size(body_size: usize) -> usize {
     let len = FIXED_PADDING_LEN + body_size;
     let pad_len = (8 - (len & 0b0111)) & 0b0111;
@@ -15,13 +18,16 @@ pub fn calc_encrypted_size(body_size: usize) -> usize {
 }
 
 /// Encrypts an arbitrary length sized data in the following way:
+///
 /// * PadLen  (1 byte)
 /// * Padding (variable, 0-7byte)
 /// * Salt    (2 bytes)
 /// * Body    (? bytes)
 /// * Zero    (7 bytes)
-/// PadLen/Padding/Salt is random bytes. Minimum of 3 bytes.
-/// PadLen is taken from the last 3 bit of the first byte.
+///
+/// Returned bytes will always have a length multiple of 8.
+///
+/// PadLen/Padding/Salt are randomly bytes, with a minimum of 21 bits (3 * 8 - 3) randomness.
 ///
 /// # Panics
 ///
@@ -78,12 +84,13 @@ pub fn encrypt<T: AsRef<[u8]>, K: AsRef<[u8]>>(plaintext: T, key: K) -> Option<B
 }
 
 /// Decrypts a byte array containing the following:
+///
 /// * PadLen  (1 byte)
 /// * Padding (variable, 0-7byte)
 /// * Salt    (2 bytes)
 /// * Body    (? bytes)
 /// * Zero    (7 bytes)
-/// PadLen/Padding/Salt is random bytes. Minimum of 3 bytes.
+///
 /// PadLen is taken from the last 3 bit of the first byte.
 pub fn decrypt<T: AsRef<[u8]>, K: AsRef<[u8]>>(encrypted: T, key: K) -> Option<Box<[u8]>> {
     let encrypted = encrypted.as_ref();