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A particular point of concern is the retention of older Bitcoin addresses that are more vulnerable due to their public keys being exposed once spent from. Early address types, known as "Pay to Public Key" (PTPK) addresses, are significantly exposed. Among approximately 1.7 million coins held in these types of addresses, around a million are attributed to Bitcoin’s enigmatic creator, Satoshi Nakamoto.
To mitigate risk, it is advised that users adopt best practices by spending the entirety of their Bitcoin from an address to avoid leaving residual funds, which leaves room for potential exposure to quantum attacks.