---
title: Address 
slug: signum/address
docTags: 
createdAt: 2022-03-31T18:50:31.000Z
---

The **Address (Reed Solomon Address**) is an [account](https://docs.signum.network/signum/account) attribute derived from the first 8 bytes of the **public key**. The address also contains the chain ID as a prefix that identifies the** blockchain network**. Therefore an address on the mainnet cannot be used on the testnet or a multiverse chain and vice versa.

:::hint{type="info"}
Entering the secret passphrase in the mainnet, testnet, or any multiverse chain based on Signum will lead to the same public key. The addresses are built with a different prefix to make it easy to see for which network the passphrase is used!

For example :

Mainnet :** S-**TTRER-GGGF-HZ56-FGGR
Testnet : **TS-**TTRER-GGGF-HZ56-FGGR
:::



## Account ID

The first 8 bytes of the public key are used to give the account ID  as a long integer. The account ID is used to create the address (Read-Solomon).

## Address structure

The short form of Signum account numbers (addresses) are of the form:  **S-XXXX-XXXX-XXXX-XXXXX**

It is the default format in the official client, where X is a non-ambiguous number or alphabetic character (the letters I and O and the numbers 1 and 0 are not used).  

Addresses are always prefixed with the corresponding blockchain ID (like “S-“for the mainnet), and hyphens are used to separate the address into 4, 4, 4, and 5 characters. The addresses are NOT case-sensitive. 

This form improves reliability by introducing redundancy to detect and correct errors when entering and using Signum account numbers.

## Background

The internal format for Signum account numbers is an entirely numeric 64-bit identifier derived from the account’s private key. This format is error-prone because a single error when typing a character can result in transactions being unintentionally sent to the wrong account.

[Reed-Solomon error-correction codes](https://en.wikipedia.org/wiki/Reed-Solomon_error_correction) primarily remedy this issue by adding redundancy to addresses.  
The Reed-Solomon format was chosen because:

- the account collision rate is the same as the default address format;
- the system’s basic error correction can be used to assist users in typing addresses;
- some programming languages do not have a native MD5 hashing function, and the Reed-Solomon implementation is more straightforward than MD5;
- the chance of a random address collision, using Signum’s implementation of 4 “check-bits,” is 1 in a million (20-bit redundancy);
- the address length is always 17 characters;
- the “S” prefix makes the addresses easily recognizable as belonging to the Signum mainnet.