# Conversions

When building applications that bridge Ethereum and Polkadot ecosystems, you'll frequently need to convert addresses between formats. The `pop convert address` command provides a reliable way to transform Ethereum addresses to Substrate/Polkadot addresses and vice versa.

You can also run the command as `pop cv address` or `pop convert a`.

## What you can use it for

* Convert Ethereum addresses to Polkadot/Substrate format for cross-chain operations.
* Transform Polkadot addresses back to Ethereum format for EVM compatibility layers.
* Generate addresses with different SS58 prefixes for various Substrate-based chains.
* Validate address formats and ensure proper cross-chain address mapping.
* Facilitate user experience in multi-chain applications by supporting both address formats.

## Quick examples

```bash
# Convert an Ethereum address to Polkadot format (default prefix 0)
pop convert address 0x742d35Cc6634C0532925a3b844Bc454e4438f44e

# Convert to a specific Substrate chain format (e.g., Kusama prefix 2)
pop convert address 0x742d35Cc6634C0532925a3b844Bc454e4438f44e 2

# Convert a Polkadot address back to Ethereum format
pop convert address 13dKz82CEiU7fKfhfQ5aLpdbXHApLfJH5Z6y2RTZpRwKiNhX

# Convert addresses from different Substrate networks
pop convert address 5Eh2qnm8NwCeDnfBhm2aCfoSffBAeMk914NUs8UDGLuoY6qg
```

## Input formats

`<ADDRESS>` can be one of:

* Ethereum address: `0x` + 40 hex characters.
* Public key: `0x` + 64 hex characters.
* Substrate address: SS58-encoded string.

## How it works

The conversion uses a standardized mapping between Ethereum and Substrate address formats:

* **Ethereum → Substrate**: Takes the 20-byte Ethereum address and extends it with 12 bytes of `0xEE` padding, then encodes it using SS58 format.
* **Substrate/Public key → Ethereum**:
  * If the last 12 bytes are `0xEE`, Pop treats it as an Ethereum-derived address and returns the first 20 bytes.
  * Otherwise, Pop computes `keccak256` of the 32-byte public key and returns the last 20 bytes.

## Output

Pop prints the converted address to stdout. Ethereum outputs are `0x`-prefixed lowercase hex.

## Errors and constraints

* Ethereum inputs must be `0x`-prefixed and exactly 40 hex characters.
* Public keys must be `0x`-prefixed and exactly 64 hex characters.
* Invalid SS58 strings fail validation.

## Tips

* **SS58 prefixes**: Different Substrate chains use different prefixes (Polkadot: 0, Kusama: 2, Generic Substrate: 42). The tool defaults to Polkadot (0) if no prefix is specified.
* **Case sensitivity**: Ethereum addresses are case-insensitive for conversion purposes.
* **Validation**: The tool validates address formats and will reject invalid inputs with clear error messages.
* **Bidirectional**: Pop automatically detects whether you're providing an Ethereum (0x-prefixed) or Substrate address and converts accordingly.
* **Cross-chain compatibility**: Only Substrate addresses originally derived from Ethereum addresses can be converted back (they must have the `0xEE` padding in the last 12 bytes).