Function salted_block_16 

pub const fn salted_block_16(
    pk_hash: [u8; 32],
    nonce: [u8; 16],
    message: [u8; 16],
) -> [u8; 64]

Constructs the exact single block pk_hash || nonce || message.

  byte 0           32         48          64
       ├───────────┼──────────┼───────────┤
       │ pk_hash   │ nonce    │ message   │   exactly one full block,
       │ 32 bytes  │ 16 bytes │ 16 bytes  │   no padding needed
       └───────────┴──────────┴───────────┘