In the context of Bitcoin and cryptocurrency, an #XFP (Extended Fingerprint) refers to a unique identifier associated with a master extended key (also known as an extended public key or xpub) in hierarchical deterministic (HD) wallets. HD wallets generate a tree-like structure of keys, where the master extended key is the root from which all other keys are derived.
Here's a technical summary of XFP:
1. **Purpose**: The XFP provides a shorthand way to identify an extended key without revealing the key itself. It's used to verify that two different #xpubs belong to the same master key.
2. **Structure**: The XFP is a 32-bit identifier (4 bytes) derived from the master extended key using a hash function. Specifically, it's the first 4 bytes of the hash160 (RIPEMD-160 after SHA-256) of the master extended key.
3. **Calculation**:
- Take the extended key (xpub).
- Perform SHA-256 hashing on the extended key.
- Perform RIPEMD-160 hashing on the SHA-256 hash.
- Take the first 4 bytes of the resulting RIPEMD-160 hash. This 4-byte value is the XFP.
4. **Use Cases**:
- **Wallet Verification**: Helps ensure that different xpubs are derived from the same master key without exposing the master key.
- **Interoperability**: When sharing xpubs between different software, the XFP helps ensure the correct xpub is used and matches the expected master key.
5. **Display**: Often displayed in hexadecimal format, making it #human-readable for comparison purposes.
### Example Workflow:
1. **Generate Master Extended Key (xpub)**:
- `xpub6CUGRUonZSQ4TWtTMmzXdrXDtypWKiKpSfey2Fv46ZoK4mKaZyCB1m9VZzmTmDBTjXbFQfz6hvWrTT4dE8YWbaqfPr5c5gZKUp7mW5Rhtq3`
2. **Compute SHA-256**:
- `SHA-256(xpub) = 9b...9c` (64-character hexadecimal string)
3. **Compute RIPEMD-160**:
- `RIPEMD-160(SHA-256(xpub)) = 50fc...d3d` (40-character hexadecimal string)
4. **Extract XFP**:
- First 4 bytes of `RIPEMD-160` hash: `50fc1234`
5. **Result**:
- XFP (Extended Fingerprint) = `50fc1234`
In summary, the XFP serves as a compact identifier for extended keys in HD wallets, enhancing security and #interoperability without revealing #sensitiveinformation #plebchain