How YSeed Generates BIP39 Seed Phrases
This page documents the mechanism behind the generator so users can inspect the process before trusting the interface.
Direct answer
YSeed generates BIP39 seed phrases by creating browser-local entropy, adding BIP39 checksum bits, splitting the result into 11-bit word indexes, and mapping those indexes to the standard English 2048-word list.
The BIP39 math in one table
| Words | Entropy | Checksum | Total bits |
|---|---|---|---|
| 12 | 128 bits | 4 bits | 132 bits |
| 15 | 160 bits | 5 bits | 165 bits |
| 18 | 192 bits | 6 bits | 198 bits |
| 21 | 224 bits | 7 bits | 231 bits |
| 24 | 256 bits | 8 bits | 264 bits |
Generation process
- Select a valid BIP39 word count: 12, 15, 18, 21, or 24 words.
- Generate entropy locally with the browser Web Crypto API.
- Add checksum bits as defined by BIP39.
- Split the entropy plus checksum stream into 11-bit chunks.
- Map each chunk to the BIP39 English 2048-word list.
- Render the phrase in memory and allow the user to wipe it from the interface.
Why YSeed avoids derivation features
Many BIP39 tools expose derivation paths, xpubs, private keys, addresses, and balance checks. Those features can be useful for advanced offline recovery work, but they increase the risk surface for a public website.
YSeed keeps the public app narrower: generate, validate, learn, and wipe. That design decision makes the product less powerful than a full wallet recovery suite, but safer for a browser-first utility.
Primary references
Methodology FAQ
What randomness source does YSeed use?
YSeed uses the browser Web Crypto API through crypto.getRandomValues(), via the BIP39 implementation used by the app. The phrase is generated in the browser, not on a server.
Why do BIP39 phrases use 11-bit chunks?
The BIP39 English wordlist has 2048 words. Because 2048 equals 2 to the 11th power, each word can represent an 11-bit index after entropy and checksum bits are combined.
Does validation prove a wallet has funds?
No. BIP39 validation only checks structure: word count, wordlist membership, and checksum. It does not prove that a wallet exists or has funds.