That's definitely a great question. If you're just playing card games, this kind of random number is sufficient. But if you're generating private keys/mnemonics, you need to pay special attention: you should draw cards as fairly and randomly as possible, repeating the process 128 times to output a relatively secure entropy (at least 128 bits). However, human shuffling and drawing might not be truly random... https://(github.com)/bitcoin/bips/blob/master/bip-0039.mediawiki generating-the-mnemonic Rolling dice is better than drawing cards like this, but you need to use dice that are as fair and random as possible. To meet the minimum security entropy requirement, you need to roll at least 50 times, because dice have 6 sides, and 6^50 is greater than 2^128. https://guide.keyst.one/zh/docs/dice-roll If you don't mind the effort, real-world random operations can be repeated multiple times. There are also professional true random service providers, like https://www.random.org, which uses atmospheric noise. But you have to trust this website... When it comes to generating private keys/mnemonics, for secure random numbers (true random or cryptographically secure pseudo-random numbers), it's recommended to adopt a realistic yet mature solution. For example, if you can truly create such a generation environment, then go for it. If not, just use a reputable hardware wallet to help you complete the process... Otherwise, you're likely to fall into a trap.