The Anchor Backlog
Open Timestamp Server anchoring worked by submitting a hash to a public ledger maintained on Earth and receiving a proof that the hash existed at a specific moment in time. The proof was cryptographic: anyone with the ledger could verify that the hash had been submitted before a certain block, and therefore that the content addressed by the hash had existed before that block.
For the first two years of the voyage, the crew submitted hashes to the Earth ledger and received proofs within an hour. The round-trip light delay was small enough that the process was nearly invisible. By year three, the delay was forty minutes each way. A hash submission took eighty minutes to yield a proof. The crew adapted by batching submissions: once a week, Fatou collected all new hashes, submitted them in a single batch, and retrieved the proofs on the next cycle.
By year five, the delay was over two hours each way. The backlog of unanchored hashes — combiners registered since the last successful batch — sometimes stretched to three hundred entries. The proofs still arrived. But the gap between 'this combiner exists' and 'this combiner is provably timestamped' had grown to five hours on a good day and twelve hours when the antenna was realigned for a course correction.
Lylia built an interim solution: a local anchoring chain. The ship maintained its own hash chain, each block containing a set of combiner hashes and a link to the previous block. The chain was not Earth-verified, but it was internally consistent. When Earth proofs arrived, Lylia's code inserted them into the chain at the appropriate block, retroactively anchoring the local records to external time.
The backlog never fully cleared. This was not a failure. The proof that a combiner existed was in the hash. The proof that it had been created before a specific moment was in the anchor chain, even if that moment was 'before block N of our local chain, which was anchored to Earth time at block M.' It was enough. It was more than most systems on Earth could say about their own history.