Update concepts-security.md

Author: nachoalonsoportillo

articles/postgresql/flexible-server/concepts-security.md

@@ -35,7 +35,7 @@ Azure Database for PostgreSQL - Flexible Server encrypts data in two ways:
    Although **it's highly not recommended**, if needed, due to legacy client incompatibility, you have an option to disable TLS\SSL for connections to Azure Database for PostgreSQL - Flexible Server by updating the `require_secure_transport` server parameter to OFF. You can also set TLS version by setting `ssl_max_protocol_version` server parameters.
 - **Data at rest**: For storage encryption, Azure Database for PostgreSQL - Flexible Server uses the FIPS 140-2 validated cryptographic module. Data is encrypted on disk, including backups and the temporary files created while queries are running.
 
-  The service uses the AES 256-bit cipher included in Azure storage encryption, and the keys are system managed. This is similar to other at-rest encryption technologies, like transparent data encryption in SQL Server or Oracle databases. Storage encryption is always on and can't be disabled.
+  The service uses [Galois/Counter Mode (GCM)](https://en.wikipedia.org/wiki/Galois/Counter_Mode) mode with AES 256-bit cipher included in Azure storage encryption, and the keys are system managed. This is similar to other at-rest encryption technologies, like transparent data encryption in SQL Server or Oracle databases. Storage encryption is always on and can't be disabled.
 
 ## Network security