Problem Statement

SHA-1 or SHA1 is a one-way hash function; it computes a 160-bit message digest. SHA-1 often appears in security protocols; for example, many HTTPS websites use RSA with SHA-1 to secure their connections. BitTorrent uses SHA-1 to verify downloads. Git and Mercurial use SHA-1 digests to identify commits. A US government standard, FIPS 180-1, defines SHA-1. Find the SHA-1 message digest for a string of octets. You may either call a SHA-1 library, or implement SHA-1 in your language. Both approaches interest Rosetta Code.

Let's start with the solution:

;;; in addition to sha1, ironclad provides sha224, sha256, sha384, and sha512.
(defun sha1-hash (data)
  (let ((sha1 (ironclad:make-digest 'ironclad:sha1))
        (bin-data (ironclad:ascii-string-to-byte-array data)))
    (ironclad:update-digest sha1 bin-data)
    (ironclad:byte-array-to-hex-string (ironclad:produce-digest sha1))))