+---------+             +---------+                          +-----+
| client  |             | server  |                          | uC  |
+---------+             +---------+                          +-----+
    |                       |                                  | ----------------
    |                       |                                  |-| stores h^n(p) |
    |                       |                                  | | and n=1000    |
    |                       |                                  | |---------------|
    |                       | ----------                      |
    |                       |-| knows p |                      |
    |                       | | and n   |                      |
    |                       | |---------|                      |
    |                       |                                  |
    | request access        |                                  |
    |---------------------->|                                  |
    |                       | ------------------              |
    |                       |-| check if access |              |
    |                       | | may be granted  |              |
    |                       | |-----------------|              |
    |                       |                                  |
    |      OTP = h^(n-1)(p) |                                  |
    |<----------------------|                                  |
    |                       |                                  |
    | OTP                   |                                  |
    |--------------------------------------------------------->|
    |                       |                                  | -----------------
    |                       |                                  |-| grant access   |
    |                       |                                  | | store OTP, n-- |
    |                       |                                  | |----------------|
    |                       |                                  |
    |                       |                   access granted |
    |                       |    if n==0: create new h^1000(p) |
    |                       |<---------------------------------|
    |                       | ----------------------          |
    |                       |-| save granted access |          |
    |                       | | n--                 |          |
    |                       | |---------------------|          |
    |                       |                                  |
    |                       | OK, h^1000(q) if needed          |
    |                       |--------------------------------->|
    |                       |                                  |