Algorithm 1 Hash value stacking algorithm

Input:  The plaintext image P and its SHA-256 hash value $V^{\left(0\right)}$ of length 32 bytes, and the key streams $Q^{\left(1\right)}$ and $Q^{\left(2\right)}$.   1:Set both $v^{\left(s\right)}$ and $v^{\left(x\right)}$ to 0;   2:for  $i=1$ to 32 do   3:   $v^{\left(s\right)}=(v^{\left(s\right)}+V^{\left(0\right)}\left(i\right))mod256$;   4:   $v^{\left(x\right)}=v^{\left(x\right)}\oplus V^{\left(0\right)}\left(i\right)$;   5:end for   6:Set $U^{\left(x\right)}=transpose\left(Q^{\left(1\right)}\right)\times Q^{\left(2\right)}$;   7:Set $U^{\left(s\right)}=v^{\left(s\right)}\times U^{\left(x\right)}$;   8:$U^{\left(x\right)}=v^{\left(x\right)}\times U^{\left(x\right)}$;   9:Set $C^{\left(1\right)}=(P+U^{\left(s\right)}+U^{\left(x\right)})mod256$ Output:  The intermediate ciphertext image $C^{\left(1\right)}$.