Message Security
The Adapter Framework does not have any special modules or services for message security.
However, you can define SecurityAttributes in the adapter metadata.
More information: ChannelAttributes, SecurityAttributes, and GlobalChannelAttributes
You can access the AS Java keystore by using the Adapter Framework APIs, which contain private and public keys for signatures or encryptions.
More information: Accessing the AS Java Keystore
You set the message security attributes in the receiver agreement.
More information:
Receiver
Agreement

For more general information about message security, see the security guide SAP NetWeaver Application Server Java Security Guide.
This contains information about security mechanisms such as keystores and existing services for digital signatures and so on.