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life_cycle-rand.7ossl - Man Page

The RAND algorithm life-cycle


All random number generator (RANDs) go through a number of stages in their life-cycle:


This state represents the RAND before it has been allocated.  It is the starting state for any life-cycle transitions.


This state represents the RAND after it has been allocated but unable to generate any output.


This state represents the RAND when it is set up and capable of generating output.


This state represents the RAND when it has been shutdown and it is no longer capable of generating output.


This state is entered when the RAND is freed.  It is the terminal state for all life-cycle transitions.

State Transition Diagram

The usual life-cycle of a RAND is illustrated:
                       |          start          |
                         | EVP_RAND_CTX_new
                       |          newed          |
                         | EVP_RAND_instantiate
   EVP_RAND_generate   +-------------------------+
 +-------------------- |                         |
 |                     |      instantiated       |
 +-------------------> |                         | <+
                       +-------------------------+  '
                         |                          '
                         | EVP_RAND_uninstantiate   ' EVP_RAND_instantiate
                         v                          '
                       +-------------------------+  '
                       |     uninstantiated      | -+
                         | EVP_RAND_CTX_free
                       |          freed          |

Formal State Transitions

This section defines all of the legal state transitions. This is the canonical list.
Function Call              ------------------ Current State ------------------
                           start   newed   instantiated  uninstantiated  freed
EVP_RAND_CTX_new           newed
EVP_RAND_instantiate            instantiated
EVP_RAND_generate                          instantiated
EVP_RAND_uninstantiate                    uninstantiated
EVP_RAND_CTX_free          freed   freed      freed          freed
EVP_RAND_CTX_get_params            newed   instantiated  uninstantiated  freed
EVP_RAND_CTX_set_params            newed   instantiated  uninstantiated  freed
EVP_RAND_CTX_gettable_params       newed   instantiated  uninstantiated  freed
EVP_RAND_CTX_settable_params       newed   instantiated  uninstantiated  freed


At some point the EVP layer will begin enforcing the transitions described herein.

See Also

provider-rand(7), EVP_RAND(3).


The provider RAND interface was introduced in OpenSSL 3.0.

Referenced By

EVP_RAND.3ossl(3), provider-mac.7ossl(7), provider-rand.7ossl(7).

2024-07-09 3.2.2 OpenSSL