message: Add notes about secure enclave feature.
diff: @@ -63,7 +63,7 @@ For async responses "Ack" commands are used.
  ### Service -> Service
  Services are completely isolated against each other, so no direct interaction between them is allowed.
  -## Special units
  +## Miscellaneous
  ### Threads Pool
  It is used by Command Executors for CPU-heavy operations. The Command Executor prepare isolated data to be computed and pass a closure to pool thread.
  @@ -72,3 +72,9 @@ While execution this closure Command Executors thread are free to process other
  ### Domain
  A set of structures definitions used while parsing incoming JSON from API of the library.
  +
  +### Secure Enclave
  +Secrets from libindy wallet are never escape from it.
  +Private keys are available only at wallet service and for Command Executors which are consuming wallet service directly.
  +Anoncreds and Crypto services consume some secrets as input for their API.
  +As a result no secrets are available above Commands Executor layer.
  