diff --git a/include/mbedtls/cipher.h b/include/mbedtls/cipher.h
index 97b9226..7ac0fd1 100644
--- a/include/mbedtls/cipher.h
+++ b/include/mbedtls/cipher.h
@@ -68,6 +68,13 @@
 extern "C" {
 #endif
 
+/**
+ * \brief     An enumeration of supported ciphers.
+ *
+ * \warning   ARC4 and DES are considered weak ciphers and their use
+ *            constitutes a security risk. We recommend considering stronger
+ *            ciphers instead.
+ */
 typedef enum {
     MBEDTLS_CIPHER_ID_NONE = 0,
     MBEDTLS_CIPHER_ID_NULL,
@@ -79,6 +86,13 @@
     MBEDTLS_CIPHER_ID_ARC4,
 } mbedtls_cipher_id_t;
 
+/**
+ * \brief     An enumeration of supported (cipher, mode) pairs.
+ *
+ * \warning   ARC4 and DES are considered weak ciphers and their use
+ *            constitutes a security risk. We recommend considering stronger
+ *            ciphers instead.
+ */
 typedef enum {
     MBEDTLS_CIPHER_NONE = 0,
     MBEDTLS_CIPHER_NULL,