Function encrypt_block 

pub fn encrypt_block<W: Word>(
    expanded_key: &[W],
    block: [W; 2],
) -> Result<[W; 2], Error>

Block Encryption

We assume that the input block is given in two w-bit registers A and B. We also assume that key-expansion has already been performed, so that the array S[0…t−1] has been computed. Here is the encryption algorithm in pseudo-code:

A = A + S[0]; B = B + S[1]; for i = 1 to r do A = ((A ⊕ B) < B) + S[2 ∗ i]; B = ((B ⊕ A) < A) + S[2 ∗ i + 1]; end for

The output is in the registers A and B.