AI Forces Diversification of Bitcoin Custody

• The 80-15-5 rule suggests 80% in cold self-custody, 15% in hot wallets, and 5% in exchanges.
• During August, the Bitcoin ecosystem suffered hacks such as those of Coldcard, ZEUS Wallet, and Boltz.

No method for storing bitcoin (BTC) is an absolute guarantee, and each of them carries its risks. This certainty became harder to ignore over the past month.

Between late July and August, a series of attacks hit various layers of the Bitcoin ecosystem, from physical wallets to exchange services, leaving a central lesson: trusting all custody to a single scheme is itself a point of exposure.

During that period, at least five platforms and products in the Bitcoin ecosystem suffered security incidents linked to the use of artificial intelligence (AI) by attackers. Among them, the theft of approximately 2,000 bitcoin (BTC) from Coldcard hardware wallets, the indefinite closure of the Boltz exchange service, and the peer-to-peer trading bot LNP2Pbot, as well as the attack on the ZEUS wallet.

On August 22, during the Latam Digital Assets Conf event held in Buenos Aires by the Growth team, Azul María Alonso, the Regional Growth Manager at the hardware wallet company Tangem, spoke exclusively with CriptoNoticias about how to distribute bitcoin holdings among various custody methods to reduce the risk of relying on just one.

The 80-15-5 Rule for Distributing Bitcoin Holdings

Alonso proposed a concrete formula during the interview for distributing bitcoin and crypto asset holdings among different custody methods, the so-called 80-15-5 rule. It is a rule proven by treasury funds, explained the Tangem executive about the origin of that proportion.

The figure indicates that 80% of the funds should be in cold self-custody, meaning in a hardware wallet disconnected from the internet, whose private keys are controlled solely by the user.

The remaining 15%, according to Alonso, should be allocated to a hot wallet, connected to the internet and more agile for interacting with decentralized finance (DeFi) protocols.

The final 5% can remain in an exchange, a centralized platform where the private keys are under the control of the company and not the user. It allows you to operate quickly, converting your bitcoin to local currency efficiently, said Alonso, mentioning Argentina as an example of a market where that liquidity is particularly useful.

Alonso clarified that the 80-15-5 rule is not a fixed norm but a flexible recommendation. Take it or leave it, she summarized about the distribution. In the specific case of Tangem's wallet, which allows operations with other networks and generates yields without leaving the same application, she suggested that the percentage in self-custody can exceed 80% without losing access to the DeFi ecosystem.

Self-Custody Remains the Safest Option, According to Alonso

Azul Alonso suggested that the concept of self-custody could evolve in the coming years as new institutional players join. Now, different actors come into play, including ETFs and all the institutionalization, she said, referring to funds and many institutional vehicles that provide exposure to bitcoin without the end investor controlling the keys.

Despite the entry of these new institutional players, Alonso maintained that her stance on self-custody does not change. There is nothing safer than having your funds in self-custody, she asserted, adding that relying on a third party means not knowing their true intentions with those funds.

Alonso supported this stance with previous episodes of platforms that hold third-party funds:

History proves itself time and again; for years, many cases have emerged of companies that hold funds and then withdrawals are paused or they declare insolvency, leaving users' funds frozen.

Azul María Alonso, Regional Growth Manager at Tangem.

However, Alonso's recommendation clashes with a real-life fact: the way most bitcoin holders in the United States manage their funds today, according to the 2025 Nakamoto Project survey. According to this study, 58.8% of American holders keep their bitcoin on an exchange, while only 23.7% have it in self-custody.

In absolute terms, this proportion equates to about 10.9 million people, just 4.21% of adults in the country, out of a total of 48.4 million bitcoin holders surveyed by the study.

The gap between the recommendation of the hardware wallet industry and the actual behavior of users is not new, but the wave of AI attacks makes it more urgent to close.

While what U.S. BTC holders do with their coins does not expose a global behavior, it is a testament that many people still trust third parties, rather than self-custody solutions.

The alternatives for holding bitcoin and cryptocurrencies highlight a central tension between security and practicality: self-custody reduces dependence on third parties but also requires the user to take responsibility for their keys and security procedures.

The 80-15-5 rule proposed by Alonso suggests a way to distribute that risk, rather than concentrating it in a single method, although it is also inevitable that people will need to spend time informing themselves and educating themselves on how to maintain their bitcoin funds, in order to make informed decisions.

Recent attacks show that no layer of the ecosystem is free from risks, so diversifying custody can be a strategy to limit the impact of a potential failure. In that scenario, the decision is not only about where to store the bitcoin but also about how much risk the user is willing to take and how they distribute their exposure.