diff --git a/docs/proposed/psa-driver-interface.md b/docs/proposed/psa-driver-interface.md
index daabad922..7851c313d 100644
--- a/docs/proposed/psa-driver-interface.md
+++ b/docs/proposed/psa-driver-interface.md
@@ -5,7 +5,7 @@ This document describes an interface for cryptoprocessor drivers in the PSA cryp
 
 This specification is work in progress and should be considered to be in a beta stage. There is ongoing work to implement this interface in Mbed TLS, which is the reference implementation of the PSA Cryptography API. At this stage, Arm does not expect major changes, but minor changes are expected based on experience from the first implementation and on external feedback.
 
-Time-stamp: "2020/08/05 20:18:29 GMT"
+Time-stamp: "2020/08/05 20:22:10 GMT"
 
 ## Introduction
 
@@ -21,7 +21,7 @@ Functions in the PSA Cryptography API invoke functions in the core. Code from th
 
 The PSA Cryptography driver interface supports two types of cryptoprocessors, and accordingly two types of drivers.
 
-* **Transparent** drivers implement cryptographic operations on keys that are provided in cleartext at the beginning of each operation. They are typically used for hardware **accelerators**. When a transparent driver is available for a particular combination of parameters (cryptographic algorithm, key type and size, etc.), it is used instead of the default software implementation. Transparent drivers can also be pure software implementations that are distributed as plug-ins to a PSA Crypto implementation.
+* **Transparent** drivers implement cryptographic operations on keys that are provided in cleartext at the beginning of each operation. They are typically used for hardware **accelerators**. When a transparent driver is available for a particular combination of parameters (cryptographic algorithm, key type and size, etc.), it is used instead of the default software implementation. Transparent drivers can also be pure software implementations that are distributed as plug-ins to a PSA Crypto implementation (for example, an alternative implementation with different performance characteristics, or a certified implementation).
 * **Opaque** drivers implement cryptographic operations on keys that can only be used inside a protected environment such as a **secure element**, a hardware security module, a smartcard, a secure enclave, etc. An opaque driver is invoked for the specific [key location](#lifetimes-and-locations) that the driver is registered for: the dispatch is based on the key's lifetime.
 
 ### Requirements