Zcash's 5 November Upgrade Would Lock About 23,000 ZEC in Sprout

Zcash's development teams are aiming to activate NU7 on 5 November, and one item in the package stops the network's oldest shielded pool from moving. The proposal is ZIP 2003, which disallows version 4 transactions. Spending from the Sprout pool needs them, so Sprout balances become unspendable at activation. ZecStats put the pool at 22,430 ZEC as of 10:16 UTC on Thursday. The coins are not destroyed, and the proposal says as much in its own text.

What the document actually says

ZIP 2003 is titled "Disallow version 4 transactions" and is still marked Draft. Its author is Daira-Emma Hopwood. The reasoning is maintenance, not money. Sprout is "essentially unused at this point", the document says, and its attack surface puts a "substantial burden on the complexity" of the protocol. Sprout was Zcash's first shielded pool, superseded by Sapling and then Orchard.

"It is not proposed in this ZIP to unissue, burn, or otherwise make Sprout funds permanently unavailable," the proposal reads.

It keeps open the option of re-enabling v4 transactions in a later upgrade, while conceding that the ability to spend may never come back. Its instruction to holders runs to one line: they "should move them out of the Sprout pool without delay."

A proposal more than two years old

This did not appear this month. The GitHub issue behind it, number 825 in the zcash/zips repository, was opened by the developer @daira on 2 May 2024. The complaint there is circuit count. "Having effectively four transaction versions (v4 to v6 and the action groups change), and five zk circuits...in the field at once is too much," the issue reads, naming Sprout JoinSplit, Sapling Spend, Sapling Output, Orchard Action and OrchardZSA Action. A separate proposal to unissue what is left in Sprout was split into its own issue and is not part of NU7.

Nobody covering it had the number

How much sits in Sprout went unreported in most of this week's write-ups. Cointelegraph and CoinMarketCap Academy both said on Wednesday that the amount is not disclosed, and KuCoin's flash, Crypto Economy and cryptoticker give no figure at all. Two sources do. ZecStats' shielded-pool dashboard reads 22,430 ZEC, against 503,000 in Sapling and 384,000 in Orchard, and describes Sprout as closing and exit-only for years. blockonomi, writing on 18 September, put it at approximately 23,000. The two agree within rounding. What neither establishes is how many notes, or how many holders, that represents.

Recovering a wallet from 2016

A forum post is doing most of the alerting. A user posting as vaspholdings on the Zcash Community Forum set out what Sprout holders need to do; the thread is dated 20 September, while Cointelegraph dates the same post to 22 September, and the two do not reconcile. Sprout addresses start with zc. Balances at zs, t1, t3 and u1 addresses are untouched. Holding the address is not enough, the post says, because the private spending key has to exist. "Do not experiment on your only copy of wallet.dat," it adds. Zcash co-founder Zooko Wilcox passed the post around on X, though neither write-up dates that.

The migration tool is z_setmigration, which moves funds out in at most five transactions per 500-block interval, with the node kept online throughout. cryptoticker, alone among the accounts read, reckons that takes days to weeks and that most exchanges moved customer Sprout balances during earlier upgrades. No exchange statement confirming that turned up.

Two dates stand between now and the freeze

Testnet activation is set for 6 October and the final call on mainnet for 20 October. No account gives a block height, or says by what procedure that call is made. NU7 also cuts block time from 75 seconds to 25 seconds and leaves the halving schedule alone, the package coinholders backed in a vote last week. ZEC rose 9% to $1,646 on Wednesday, a long way past the $1,200 it cleared on 7 September. At that price the pool is worth tens of millions of dollars. Whether anyone still holds the spending keys to it is the part no dashboard shows.