openpgp: Improve documentation.

1 files changed, 5 insertions, 0 deletions

diff --git a/openpgp/src/crypto/asymmetric.rs b/openpgp/src/crypto/asymmetric.rs
index 9a497f9a..9c8a1ae6 100644
--- a/openpgp/src/crypto/asymmetric.rs
+++ b/openpgp/src/crypto/asymmetric.rs
@@ -7,6 +7,11 @@ use constants::HashAlgorithm;
 use Result;
 
 /// Creates a signature.
+///
+/// This is a low-level mechanism to produce an arbitrary OpenPGP
+/// signature.  Using this trait allows Sequoia to perform all
+/// operations involving signing to use a variety of secret key
+/// storage mechanisms (e.g. smart cards).
 pub trait Signer {
     /// Returns a reference to the public key.
     fn public(&self) -> &Key;