In the process of making a cold wallet, you must ensure that the mnemonic phrase is truly random. If it is pseudo-random, there is a possibility of brute force cracking. The usual approach is to choose a trustworthy open source wallet to generate it, but some people still cannot give up their concerns. Is there any way to manually select a mnemonic randomly without relying on software? I saw a tutorial on the Internet. The first 11 digits are randomly selected. For example, by throwing dice, the first 11 mnemonics are randomly found. The last mnemonic is the check digit. Randomly try one by one, no more than 30 times. You can find a suitable check word. I did an experiment and selected the first 11 letters of the github mnemonic vocabulary, and tried the twelfth letters one by one until I tried more than ten times until I succeeded in trying the actress letters. Of course, this kind of pseudo-random wallet is extremely insecure. You can also generate mnemonic words manually by experimenting without relying on any third-party software.