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+# Remove arbitrary bytes
+A leaf's checksum is currently an opaque array of 32 arbitrary bytes.  We would
+like to change this to H(checksum), so that no logged bytes are arbitrary.  As a
+result, the threat of log poisoning goes from unlikely to very unlikely.
+
+## Details
+New leaf:
+- Shard hint
+- H(checksum), was "just checksum"
+- Signature
+- H(public key)
+
+A signer's signed statement must be for H(checksum), not checksum.  In other
+words, a signer basically signs H(H(data)), then checksum<-H(data) is submitted
+on our current add-leaf endpoint.  The log computes H(checksum) for incoming
+add-leaf requests.  No other changes are required for the log's leaf endpoints.
+
+Monitors locate data externally based on H(checksum), not checksum.  Note that
+monitors can verify observed signatures as before without locating the data.
+This is important so that we can be sure a signing operation actually happened.
+
+Verifiers need the same (meta)data distributed, but in the verification step
+H(checksum) must be computed to verify signatures and inclusion proofs.
+
+Witnesses are not affected by this change.
+
+## Other
+A different approach would be to submit data and let the log hash that.  Not
+letting the log see data is a feature:
+- The data cannot be analyzed by the log unless its location is known
+- The data cannot be expected to be stored in the future
+- Each logging request becomes cheaper