The minimum value for a key identifier that is built into the implementation. The range of key identifiers from #MBEDTLS_PSA_KEY_ID_BUILTIN_MIN to #MBEDTLS_PSA_KEY_ID_BUILTIN_MAX within the range from #PSA_KEY_ID_VENDOR_MIN and #PSA_KEY_ID_VENDOR_MAX and must not intersect with any other set of implementation-chosen key identifiers. This value is part of the library's ABI since changing it would invalidate the values of built-in key identifiers in applications.