crypto

User's Guide

Version 4.2.1

- User's Guide
- Reference Manual
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### Chapters

- Licenses
  - Top of chapter
  - OpenSSL License
  - SSLeay License
- FIPS mode
  - Top of chapter
  - Background
  - Enabling FIPS mode
  - Incompatibilities with regular builds
  - Common caveats
- Engine Load
  - Top of chapter
  - Background
  - Use Cases
- Engine Stored Keys
  - Top of chapter
  - Background
  - Use Cases

# 3 Engine Load

This chapter describes the support for loading encryption engines in the crypto application.

### 3.1 Background

OpenSSL exposes an Engine API, which makes it possible to plug in alternative implementations for some or all of the cryptographic operations implemented by OpenSSL. When configured appropriately, OpenSSL calls the engine's implementation of these operations instead of its own.

Typically, OpenSSL engines provide a hardware implementation of specific cryptographic operations. The hardware implementation usually offers improved performance over its software-based counterpart, which is known as cryptographic acceleration.

### 3.2 Use Cases

#### Dynamically load an engine from default directory

If the engine is located in the OpenSSL/LibreSSL installation engines directory.

    1> {ok, Engine} = crypto:engine_load(<<"otp_test_engine">>, [], []).
     {ok, #Ref}

Note

The file name requirement on the engine dynamic library can differ between SSL versions.

#### Load an engine with the dynamic engine

Load an engine with the help of the dynamic engine by giving the path to the library.

     2> {ok, Engine} = crypto:engine_load(<<"dynamic">>,
                                          [{<<"SO_PATH">>,
                                            <<"/some/path/otp_test_engine.so">>},
                                           {<<"ID">>, <<"MD5">>},
                                           <<"LOAD">>],
                                          []).
     {ok, #Ref}

Note

The dynamic engine is not supported in LibreSSL from version 2.2.1

#### Load an engine and replace some methods

Load an engine with the help of the dynamic engine and just replace some engine methods.

     3> Methods = crypto:engine_get_all_methods() -- [engine_method_dh,engine_method_rand,
    engine_method_ciphers,engine_method_digests, engine_method_store,
    engine_method_pkey_meths, engine_method_pkey_asn1_meths].
    [engine_method_rsa,engine_method_dsa,
     engine_method_ecdh,engine_method_ecdsa]
     4> {ok, Engine} = crypto:engine_load(<<"dynamic">>,
                                          [{<<"SO_PATH">>,
                                            <<"/some/path/otp_test_engine.so">>},
                                           {<<"ID">>, <<"MD5">>},
                                           <<"LOAD">>],
                                          [],
    		                      Methods).
     {ok, #Ref}

#### List all engines currently loaded

     5> crypto:engine_list().
    [<<"dynamic">>, <<"MD5">>]