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+## Private declarations
+
+Sample programs have not been fully updated yet and some of them might still
+use APIs that are no longer public. You can recognize them by the fact that they
+define the macro `MBEDTLS_DECLARE_PRIVATE_IDENTIFIERS` (or
+`MBEDTLS_ALLOW_PRIVATE_ACCESS`) at the very top (before including headers). When
+you see one of these two macros in a sample program, be aware it has not been
+updated and parts of it do not demonstrate current practice.
+
+We strongly recommend against defining `MBEDTLS_DECLARE_PRIVATE_IDENTIFIERS` or
+`MBEDTLS_ALLOW_PRIVATE_ACCESS` in your own application. If you do so, your code
+may not compile or work with future minor releases. If there's something you
+want to do that you feel can only be achieved by using one of these two macros,
+please reach out on github or the mailing list.