diff --git a/crypto/scrypt/lib/README b/crypto/scrypt/lib/README
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+The source code under this directory is taken from the client for the
+Tarsnap online backup system (and released under the 2-clause BSD license
+with permission of the author); keeping this code in sync with the Tarsnap
+code is highly desirable and explains why there is some functionality
+included here which is not actually used by the scrypt file encryption
+utility.