Address

Bitmessage adresses are Base58 encoded public key hashes. An address looks like BM-BcbRqcFFSQUUmXFKsPJgVQPSiFA3Xash. All Addresses start with BM-, however clients should accept addresses without the prefix. PyBitmessage does this. The reason behind this idea is the fact, that when double clicking on an address for copy and paste, the prefix is usually not selected due to the dash being a common separator.

Public Key usage
Addresses may look complicated but they fulfill the purpose of verifying the sender. A Message claiming to be from a specific address can simply be checked by decoding a special field in the data packet with the public key, that represents the address. If the decryption succeeds, the message is from the address it claims to be.

Length
Without the BM- prefix, an address is usually 32-34 chars long. Since an address is a hash it can be calculated by the client in a way, that the first bytes are zero (\0) and bitmessage strips these. This causes the client to do much more work to be lucky and find such an address. This is an optional checkbox in PyBitmessage.

Versions

 * v1 addresses used a single RSA key pair (see the pubkey structure here: https://bitmessage.org/w/index.php?title=Protocol_specification&oldid=23 )
 * v2 addresses use 2 ECC key pairs
 * v3 addresses extends v2 addresses to allow specifying the proof of work requirements. The pubkey object is signed to mitigate against forgery/tampering.
 * v4 addresses protect against harvesting addresses from getpubkey and pubkey objects (see https://bitmessage.org/forum/index.php?topic=2975.0 for details of a harvesting attack)

Since v1 addresses are no longer used https://www.bitmessage.org/wiki/Protocol_specification#pubkey serves as a reference

Address Types
There are two address types the user can generate in PyBitmessage. The resulting addresses have no difference, but the method how they are created differs.

Deterministic Address
For this type of Address a passphrase is required, that is used to seed the random generator. Using the same passphrase creates the same addresses. Using deterministic addresses should be done with caution, using a word from a dictionary or a common number can lead to others generating the same address and thus being able to receive messages not intended for them. Generating a deterministic address will not publish the public key. The key is sent in case somebody requests it. This saves POW time, when generating a bunch of addresses.

Usage
 * Create the same address on multiple systems without the need of copying keys.dat or an Address Block.
 * create a Decentralized Mailing List. (Use the Join/create chan option in the file menu instead)
 * Being able to restore the address in case of address database corruption or deletation.

Random Address
Random addresses are generated from a randomly chosen number. The resulting address cannot be regenerated without knowledge of the number and therefore the keys.dat should be backed up. Generating random addresses takes slightly longer due to the POW required for the public key broadcast.

Usage
 * Generate unique addresses
 * Generate one time addresses.

Recovering/Regenerating/Recreating an Address
You can recreate an address in multiple clients without having to move any files between them by using Deterministic Addresses.

Usage
 * Generate a Deterministic Address and remember all of the selections made when doing so.
 * On another Bitmessage client navigate to:
 * File > Regenerate deterministic addresses
 * Re-enter the data that you used to create the original Deterministic Address

Note: Be sure to use a passphrase that is not easy to duplicate. Anyone that use the same passphrase (and other settings) will generate the same address.

Related pages
Public key to bitmessage address; Find the address for a given public key