A                       B
                |                       |
                |                       |
  (compute pA)  |          pA           |
                |---------------------->|
                |          pB           | (compute pB)
                |<----------------------|
                |                       |
                |   (derive secrets)    |
                |                       |
  (compute cA)  |          cA           |
                |---------------------->|
                |          cB           | (compute cB)
                |                       | (check cA)
                |<----------------------|
  (check cB)    |                       |