C-Lock: Local Network Resilient Port Knocking System Based on TOTP

Algorithm 1

Port generation algorithm.

Initialization

1: tSlot ← epochT imestamp()//30           {//means integer division}

2: totp ← hotp(tSlot, sk)           {e.g.123456}

Strategy A

1: forn ←0to 3 do

2:begin

3:aux ← hotp(n, totp)

4:port[n] ← (aux%65534) +1           {0 < port<65535}

5:end

Strategy B

1: mask ← 0xC030           {0xC030 = 49200}

^2:paux^{[0] ← (totp//1e4)           {e.g.12}}

^3:paux^{[1] ← (totp//1e2) − (p}aux^{[0]1e2)           {e.g.34}}

^4:paux^{[2] ← (totp) − (p}aux^{[1]1e2) − (p}aux^{[0]1e4)           {e.g.56}}

5: forn ←0to 3 do

6:begin

7:port[n] ← mask + paux[n]         {port[0] = 0xC030+12 = 49212}

8:end