diff --git a/README.md b/README.md
new file mode 100644
--- /dev/null
+++ b/README.md
@@ -0,0 +1,10 @@
+_Format-preserving encryption_ encrypts data without changing its
+format.  An example is encrypting a 16-digit credit card number
+as 16 digits.  The encryption uses a key, which is secret, and an
+optional _tweak_, which can be public and varies for each record
+(such as the cardholder's name), and provides extra security.
+
+This module implements FF1.  Another similar algorithm, FF3, is no
+longer considered secure, and so is not included (yet).
+
+For example usage, see `ff1test.hs`.
diff --git a/fpe.cabal b/fpe.cabal
--- a/fpe.cabal
+++ b/fpe.cabal
@@ -1,13 +1,13 @@
-cabal-version: 1.12
+cabal-version: 1.18
 
 -- This file has been generated from package.yaml by hpack version 0.31.1.
 --
 -- see: https://github.com/sol/hpack
 --
--- hash: 8fbbdfc71a8796c3cda5555879b81de5510d7c2662c55142ea49394a54df5cdb
+-- hash: e71c8a5c25b6f4d91367a858231df53931e152636540804b099f15ac62d85392
 
 name:           fpe
-version:        0.1.0
+version:        0.1.1
 synopsis:       Format-preserving encryption.
 category:       Cryptography
 homepage:       https://github.com/galenhuntington/fpe#readme
@@ -16,6 +16,8 @@
 license:        MIT
 license-file:   LICENSE
 build-type:     Simple
+extra-doc-files:
+    README.md
 
 source-repository head
   type: git