Quote from: alexkrypto on June 07, 2020, 11:21:15 AM

- Which way is better? generating seed phrase using ian coleman offline then restore it on trezor to ensure Xpub is not leaked to ISP or any VPN, or to use Electrum offline with Trezor to generate seed phrase?

To achieve full anonymity it is better to generate your mnemonic phrase manually, without using online or offline tools whatsoever since they can be still compromised. However, this approach is rather for paranoids. In order to manually create mnemonic phrase, you first have to generate a decent level of entropy by flipping a coin 256 times, for example. Then you have to find a checksum for this entropy and this is the hardest part. Checksum is the first 8 bits of SHA-256 hash of your big 256 binary number. It is possible to hash numbers by hand, there are many guides on the internet on how to do that.

Useful links:
https://medium.com/coinmonks/mnemonic-generation-bip39-simply-explained-e9ac18db9477
https://crypto.stackexchange.com/questions/50993/sha-256-by-hand
https://www.quora.com/How-is-it-possible-to-calculate-and-do-a-SHA-2-hash-by-hand-so-I-know-that-the-NSA-is-not-fooling-everyone
https://hackaday.com/2014/09/29/mining-bitcoins-with-pencil-and-paper/#more-133640