Owning bitcoins (or sats: 1 sat or satoshi is 1/100,000,000 of a bitcoin) means having control over the private keys necessary to authorize transactions within the blockchain (the public and decentralized ledger where Bitcoin 'lives'). These keys, along with other wallet information, are hierarchically and deterministically derived from: 

1. a "seed phrase" (or "mnemonic"): typically a set of 12 or 24 words, depending on the wallet's configuration ("BIP32" wallets have 12 words and "BIP39" wallets have 24 words, but there are also other configurations);

2. an optional passphrase: often referred to as the "25th word", this is available only with 24-word seeds ("BIP39" wallets), adding extra security;

3. a derivation path determining the structure of key generation. Intuitively, the derivation path is like the specific 'pocket' of the wallet where we decide to keep our coins. It is usually standard ("BIP32" or "BIP44") but it can be customized.

Whoever has access to these three pieces of information controls the bitcoins. It is therefore fundamental:

​

1. that this information is generated in a secure way;

2. that, after having been generated, this information is kept secret and protected;

3. that this information is kept in a support that does not deteriorate with time;

4. that this information is kept in a support that doesn't break easily;

5. that this information is not lost (and/or that it is backed up);

6. that this information is stored in such a way to divert a direct attack;

7. that this information is geographically dispersed in such a way that a direct attack, even when successful, cannot compromise it;

8. that secure and trustless arrangements are made for this information to arrive at the desired person(s) in case of unforeseen accident. This topic will not be discussed in this course.

​

What we studied in Course 1 helps doing some of these things pretty well. What we'll study in this Course 2 helps doing the rest of them pretty well.

In addition, and more in general, the scope of this Course 2 is to help the non-expert managing and storing his bitcoins privately and securely.During this course, it will be assumed that the reader masters all the techniques and tools illustrated during Course 1. In particular, it will be assumed that he/she uses Tails OS and its pre-installed password manager (KeePassXC).Unless explicitly stated, all operations will be done in a secure and cold computer.

• operations that have to be done in a secure and cold computer are marked with "°";

• operations that have to be done in a hot computer (i.e. a computer connected to the Internet) are marked with "^";

• operations that have to be done with two computers (one of which secure and cold, the other hot) are marked with "°^".