A first study of improving transposition cryptosystem
H. B. Bahar, Mohsen Sokouti, Babak Sokouti · Journal of Discrete Mathematical Sciences and Cryptography · 2010
Transposition ciphers are stronger than simple substitution ciphers. However, if the key is short and the message is long, then various cryptanalysis techniques can be applied to break such ciphers. By adding 8 bits (one byte) for each byte using a function and a binary tree, we can make this cipher protected. Using an inorder tour on binary tree can diffuse the eight bits and eight bits of a byte of plaintext. This can highly protect the cipher however, if the key management processes are not secure the strongest ciphers can easily broken.