Add ChangeLog entry for the DRBG documentation improvements
diff --git a/ChangeLog b/ChangeLog
index a746a38..88b9345 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
mbed TLS ChangeLog (Sorted per branch, date)
+= mbed TLS 2.7.x branch released xxxx-xx-xx
+
+Changes
+ * Clarify how the interface of the CTR_DRBG and HMAC modules relates to
+ NIST SP 800-90A. In particular CTR_DRBG requires an explicit nonce
+ to achieve a 256-bit strength if MBEDTLS_ENTROPY_FORCE_SHA256 is set.
+
= mbed TLS 2.7.12 branch released 2019-09-06
Security