MESH is actually a family of 3 variant ciphers with block sizes of 64, 96, and 128 bits. The key size is twice the block size. The number of rounds is 8.5, 10.5, or 12.5, depending on the block size. The algorithm uses a Lai-Massey scheme based on IDEA's, but with a larger round structure, or "MA-box". MESH also has a more complex key schedule than IDEA, intended to prevent weak keys and other insecure patterns in subkeys.