From 9d4d218eef62a64e1596f0208a7af674785efb38 Mon Sep 17 00:00:00 2001
From: Hans Nilsson <hans@erlang.org>
Date: Thu, 21 Mar 2019 11:59:25 +0100
Subject: crypto: Note about key lengths for cipher_info/1

---
 lib/crypto/doc/src/crypto.xml | 9 +++++++++
 1 file changed, 9 insertions(+)

(limited to 'lib')

diff --git a/lib/crypto/doc/src/crypto.xml b/lib/crypto/doc/src/crypto.xml
index 251263714d..64872d7414 100644
--- a/lib/crypto/doc/src/crypto.xml
+++ b/lib/crypto/doc/src/crypto.xml
@@ -917,6 +917,15 @@
 	<p>Provides a map with information about block_size, key_length, iv_length and possibly other properties of the
 	cipher algorithm in question.
 	</p>
+        <note>
+	  <p>The ciphers <c>aes_cbc</c>, <c>aes_cfb8</c>, <c>aes_cfb128</c>, <c>aes_ctr</c>, 
+	  <c>aes_ecb</c>, <c>aes_gcm</c> and <c>aes_ccm</c>
+	  has no keylength in the <c>Type</c> as opposed to for example <c>aes_128_ctr</c>. They adapt to the length of
+	  the key provided in the encrypt and decrypt function. Therefor it is impossible to return a valid keylength
+	  in the map.</p>
+	  <p>Always use a <c>Type</c> with an explicit key length,
+	  </p>
+	</note>
 	<p>For a list of supported cipher algorithms, see <seealso marker="#supports-0">supports/0</seealso>.
 	</p>
       </desc>
-- 
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