Curriculum·Freshman·F103
Keys, Addresses, and What Custody Means
A survey of 1,000 US crypto holders, run by Oobit through the CloudResearch Connect panel and released on 29 April 2026, found 35 percent had lost access to a wallet or account, and 31 percent of those never recovered the funds. The leading causes were a forgotten password (33 percent), a lost recovery phrase (21 percent) and lost access to two-factor authentication (20 percent).
Lesson 1 opens on
Profanity and Wintermute, September 2022
Profanity was a popular tool for generating vanity addresses, meaning addresses with a chosen prefix such as a run of zeroes.3 billion. Analysts estimated that around 1,000 GPUs could brute force every 7-character vanity address in about 50 days.
The lessons
- F103-01The key chainOrder the four objects correctly, from entropy through private key and public key to address, and state which direction is computableabout 30 min · opens on Profanity and Wintermute, September 2022
- F103-02Seed phrasesExplain what the words are, how many bits each carries, and what the final word is doingabout 31 min · opens on Milk Sad, CVE-2023-39910
- F103-03Custodial vs self-custodialDetermine which arrangement you are in by asking who can sign, rather than by what the product is calledabout 24 min · opens on Celsius Earn accounts, ruling January 2023
- F103-04Smart accounts and account abstractionDistinguish an externally owned account from a smart account by what decides whether a transaction is validabout 31 min · opens on The Parity multisig freeze, November 2017
- F103-05The new risk surfaceExplain why a delegation is categorically more dangerous than a token approval, and state the scope of eachabout 31 min · opens on EIP-7702 delegation phishing, 2025
Labs
F103-L
Take a throwaway seed generated for the sitting, derive the same address at the standard path in two wallets, then change the path and watch a different empty address appear. Four addresses to produce and one explanation of what happened. Never fund the seed.