As much as $23 million worth of crytocurrency may have been stolen in a recent hack of Christchurch-based Cryptopia, according to an analysis from New York-based blockchain infrastructure firm Elementus.
Police were advised last week of an issue involving potential unauthorised transaction activity after Cryptopia announced it had suffered a security breach which resulted in significant losses.
According to Elementus, data on the Ethereum public blockchain indicates that funds began to be siphoned from Cryptopia's two core wallets — one holding ETH, the other tokens — on the morning of January 13.
Elementus calculates that just under US$3.6m ($5.3m) in ETH was stolen, about US$2.4m of Dentacoin, almost US$2m in Oyster Pearl, and about US$3m in unspecified other tokens.
"The funds were taken from more than 76,000 different wallets, none of which were smart contracts. The thieves must have gained access to not one private key, but thousands of them," Elementus analyst Max Galka wrote on a blog.
Meanwhile, Police are drawing on international expertise as they investigate the theft.
Those international contacts include members of the cryptocurrency trading community, Police said in a statement updating progress to date.
"This is a very complex investigation, involving expert digital forensic investigators from within New Zealand and in various overseas jurisdictions, as well as overseas authorities.
"Members of the investigation team met with Cryptopia management and staff yesterday and today and outlined progress in the investigation."
At least $3.5m-worth of the funds hacked on the night of January 13-14 are visible in one digital wallet.
Some money sent from the visible wallet to the giant international cryptocurrency exchange Binance has been frozen by that exchange.
Police say Cryptopia management and staff have been cooperating and have provided considerable assistance in the investigation.
"The investigation is expected to take some to time complete, and the digital forensic team will be on-site at Cryptopia's premises for some days to come," the statement said.