Difference between revisions of "Address"

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(bitcoin address is a encoded hashvalue of a public key!)
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A '''Bitcoin address''', or simply '''address''', is an identifier of 27-34 alphanumeric characters, beginning with the number 1 or 3, that represents a possible destination for a Bitcoin payment. Effectively it is a 20-bytes long hash from the [[RIPEMD160]] function of a public key encoded into alphanumeric characters.
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A '''Bitcoin address''', or simply '''address''', is an identifier of 26-35 alphanumeric characters, beginning with the number <code>1</code>, <code>3</code> or <code>bc1</code> that represents a possible destination for a bitcoin payment.
 
Addresses can be generated at no cost by any user of Bitcoin.
 
Addresses can be generated at no cost by any user of Bitcoin.
For example, using [[Bitcoin-Qt]], one can click "New Address" and be assigned an address.
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For example, using [[Bitcoin Core]], one can click "New Address" and be assigned an address.
 
It is also possible to get a Bitcoin address using an account at an exchange or online wallet service.
 
It is also possible to get a Bitcoin address using an account at an exchange or online wallet service.
  
An example of a Bitcoin address is ''31uEbMgunupShBVTewXjtqbBv5MndwfXhb''.
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There are currently three [[List_of_address_prefixes|address formats]] in use:
<!-- Note: This bitcoin address is based on ripemd160(sha256('Bitcoin')) with version 5 and a corrupt checksum -->
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# [[Transaction#Pay-to-PubkeyHash|P2PKH]] which begin with the number <code>1</code>, eg: <code>1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2</code>.<!-- tails donation address -->
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# [[Pay_to_script_hash|P2SH]] type starting with the number <code>3</code>, eg: <code>3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy</code><!-- anyone-can-spend, null script -->.
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# [[Bech32]] type starting with <code>bc1</code>, eg: <code>bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq</code>.<!--some example LN wallet-->
  
==A Bitcoin address is like an e-mail address==
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==A Bitcoin address is a single-use token==
Like e-mail, you can send bitcoins to a person by sending bitcoins to one of their addresses. A person can have many different Bitcoin addresses and, for increased privacy and as the only way to know what the bitcoins are received for/from, it is recommended that you use a unique address for each transaction. Most Bitcoin software and websites will help with this by generating a brand new address each time you perform a transaction. Some services provide a facility to request a new Bitcoin address for use with their service when desired.
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Like e-mail addresses, you can send bitcoins to a person by sending bitcoins to one of their addresses.
 
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However, ''unlike'' e-mail addresses, people have many different Bitcoin addresses and a unique address should be used for each transaction.
When using a web site that accepts bitcoins or holds Bitcoin balances on your behalf, that website will assign a Bitcoin address to your account, so you can transfer funds into your account at the site.  Very much unlike e-mail, this address may change every time funds come in so care should be taken when sending additional funds to a previously-used address.  When you send Bitcoins to your account at a web site, they will usually be credited to your account at that web site after the transaction is [[confirmation|confirmed]].
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Most Bitcoin software and websites will help with this by generating a brand new address each time you create an invoice or payment request.
  
 
==Addresses can be created offline==
 
==Addresses can be created offline==
Creating addresses can be done without an Internet connection and does not require any contact or registration with the Bitcoin network. The network starts tracking an address when it is first seen in a valid payment transaction.
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Creating addresses can be done without an Internet connection and does not require any contact or registration with the Bitcoin network.
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It is possible to create large batches of addresses offline using freely available software tools.
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Generating batches of addresses is useful in several scenarios, such as e-commerce websites where a unique pre-generated address is dispensed to each customer who chooses a "pay with Bitcoin" option.
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Newer [[Deterministic wallet | "HD wallets"]] can generate a "master public key" token which can be used to allow untrusted systems (such as webservers) to generate an unlimited number of addresses without the ability to spend the bitcoins received.
  
It is possible to create large batches of addresses offline using freely available software toolsGenerating batches of addresses is useful in several scenarios, such as e-commerce websites where a unique pre-generated address is dispensed to each customer who chooses a "pay with Bitcoin" option.
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==Addresses are often case sensitive and exact==
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Old-style Bitcoin addresses are case-sensitiveBitcoin addresses should be copied and pasted using the computer's clipboard wherever possible. If you hand-key a Bitcoin address, and each character is not transcribed exactly - including capitalization - the incorrect address will most likely be rejected by the Bitcoin software.  You will have to check your entry and try again.
  
An average desktop computer can generate thousands of new Bitcoin addresses a minute.  Addresses are created simply by generating random numbers and then performing mathematical operations to derive matching pairs of "public" and "private" keys.  Because addresses can be created easily and at minimal cost, it is not uncommon to create temporary addresses that can be discarded if unused.
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The probability that a mistyped address is accepted as being valid is 1 in 2<sup>32</sup>, that is, approximately 1 in 4.29 billion.
  
==Addresses are case sensitive and exact==
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New-style [[bech32]] addresses are case insensitive.
Bitcoin addresses are case-sensitive.  Bitcoin addresses should be copied and pasted using the computer's clipboard wherever possible. If you hand-key a Bitcoin address, and each character is not transcribed exactly - including capitalization - the incorrect address will most likely be rejected by the Bitcoin software.  You will have to check your entry and try again.
 
  
The probability that a mistyped address is accepted as being valid is 1 in 2<sup>32</sup>, that is, approximately 1 in 4.29 billion.
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==Proving you receive with an address==
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Most Bitcoin wallets have a function to "sign" a message, proving the entity receiving funds with an address has agreed to the message.
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This can be used to, for example, finalise a contract in a cryptographically provable way prior to making payment for it.
  
==Address validation==
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Some services will also piggy-back on this capability by dedicating a specific address for authentication only, in which case the address should never be used for actual Bitcoin transactions.
If you would like to validate a Bitcoin address in an application, it is advisable to use a method from [https://bitcointalk.org/index.php?topic=1026.0 this thread] rather than to just check for string length, allowed characters, or that the address starts with a 1 or 3.
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When you login to or use their service, you will provide a signature proving you are the same person with the pre-negotiated address.
  
==Addresses have a "private key"==
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It is important to note that these signatures only prove one receives with an address.
For most properly-generated Bitcoin addresses, there is at least one secret number known as a [[private key]] which is required for access to the funds assigned to that address.
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Since Bitcoin transactions do not have a "from" address, you cannot prove you are the ''sender'' of funds.
  
When using a Bitcoin client, private keys are typically stored in the [[Wallet|wallet file]].  The private key has a special purpose - it is mathematically needed to create valid transactions that spend the funds originally sent to the address.  If the private key to an address is lost (for example, in a hard drive crash, fire or other natural disaster), any associated Bitcoins are effectively lost forever.
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Current standards for message signatures are only compatible with "version zero" bitcoin addresses (that begin with the number 1).
  
==Multi-signature addresses==
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==Address validation==
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If you would like to validate a Bitcoin address in an application, it is advisable to use a method from [https://bitcointalk.org/index.php?topic=1026.0 this thread] rather than to just check for string length, allowed characters, or that the address starts with a 1 or 3.  Validation may also be done using open source code available in [http://rosettacode.org/wiki/Bitcoin/address_validation various languages] or with an [http://lenschulwitz.com/base58 online validating tool].
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==[[Multisignature|Multi-signature]] addresses==
 
Addresses can be created that require a combination of multiple private keys.
 
Addresses can be created that require a combination of multiple private keys.
 
Since these take advantage of newer features, they begin with the newer prefix of 3 instead of the older 1.
 
Since these take advantage of newer features, they begin with the newer prefix of 3 instead of the older 1.
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They consist of random digits and uppercase and lowercase letters, with the exception that the uppercase letter "O", uppercase letter "I", lowercase letter "l", and the number "0" are never used to prevent visual ambiguity.
 
They consist of random digits and uppercase and lowercase letters, with the exception that the uppercase letter "O", uppercase letter "I", lowercase letter "l", and the number "0" are never used to prevent visual ambiguity.
  
Some Bitcoin addresses can be shorter than 34 characters (as few as 27 in theory) and still be valid.
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Some Bitcoin addresses can be shorter than 34 characters (as few as 26) and still be valid.
 
A significant percentage of Bitcoin addresses are only 33 characters, and some addresses may be even shorter.
 
A significant percentage of Bitcoin addresses are only 33 characters, and some addresses may be even shorter.
Every Bitcoin address stands for a number - somewhat like an account number. These shorter addresses are valid simply because they stand for numbers that happen to start with zeroes, and when the zeroes are omitted, the encoded address gets shorter.
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Every Bitcoin address stands for a number.
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These shorter addresses are valid simply because they stand for numbers that happen to start with zeroes, and when the zeroes are omitted, the encoded address gets shorter.
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 +
Several of the characters inside a Bitcoin address are used as a checksum so that typographical errors can be automatically found and rejected.
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The checksum also allows Bitcoin software to confirm that a 33-character (or shorter) address is in fact valid and isn't simply an address with a missing character.
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==Testnet==
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Addresses on the Bitcoin Testnet are generated with a different address version, which results in a different prefix.
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See [[List of address prefixes]] and [[Testnet]] for more details.
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==Misconceptions==
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===Address reuse===
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Addresses are not intended to be used more than once, and doing so has numerous problems associated.
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See the dedicated article on [[address reuse]] for more details.
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 +
===Address balances===
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Addresses are not wallets nor accounts, and do not carry balances.
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They only receive funds, and you do not send "from" an address at any time.
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Various confusing services and software display ''bitcoins received with an address, minus bitcoins sent in random unrelated transactions'' as an "address balance", but this number is not meaningful: it does not imply the recipient of the bitcoins sent to the address has spent them, nor that they still have the bitcoins received.
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An example of bitcoin loss resulting from this misunderstanding is when people believed their address contained 3btc. They spent 0.5btc and believed the address now contained 2.5btc when actually it contained zero. The remaining 2.5btc was transferred to a change address which was not backed up and therefore lost. This has happened on a few occasions to users of [[Paper wallets]].
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==="From" addresses===
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Bitcoin transactions do not have any kind of origin-, source- or "from" address. See the dedicated article on "[[From address|from address]]" for more details.
 +
 
 +
 
 +
==Address map==
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[[File:Address map.jpg|700px]]
  
Several of the characters inside a Bitcoin address are used as a checksum so that typographical errors can be automatically found and rejected.  The checksum also allows Bitcoin software to confirm that a 33-character (or shorter) address is in fact valid and isn't simply an address with a missing character.
 
  
 
==See Also==
 
==See Also==
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* [[List of address prefixes]]
 
* [[List of address prefixes]]
 
* [[Exit Address]]
 
* [[Exit Address]]
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== References ==
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<references/>
  
 
[[Category:Vocabulary]]
 
[[Category:Vocabulary]]
  
 
[[es:Dirección]]
 
[[es:Dirección]]
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[[de:Adresse]]

Latest revision as of 09:10, 8 May 2019

A Bitcoin address, or simply address, is an identifier of 26-35 alphanumeric characters, beginning with the number 1, 3 or bc1 that represents a possible destination for a bitcoin payment. Addresses can be generated at no cost by any user of Bitcoin. For example, using Bitcoin Core, one can click "New Address" and be assigned an address. It is also possible to get a Bitcoin address using an account at an exchange or online wallet service.

There are currently three address formats in use:

  1. P2PKH which begin with the number 1, eg: 1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2.
  2. P2SH type starting with the number 3, eg: 3J98t1WpEZ73CNmQviecrnyiWrnqRhWNLy.
  3. Bech32 type starting with bc1, eg: bc1qar0srrr7xfkvy5l643lydnw9re59gtzzwf5mdq.

A Bitcoin address is a single-use token

Like e-mail addresses, you can send bitcoins to a person by sending bitcoins to one of their addresses. However, unlike e-mail addresses, people have many different Bitcoin addresses and a unique address should be used for each transaction. Most Bitcoin software and websites will help with this by generating a brand new address each time you create an invoice or payment request.

Addresses can be created offline

Creating addresses can be done without an Internet connection and does not require any contact or registration with the Bitcoin network. It is possible to create large batches of addresses offline using freely available software tools. Generating batches of addresses is useful in several scenarios, such as e-commerce websites where a unique pre-generated address is dispensed to each customer who chooses a "pay with Bitcoin" option. Newer "HD wallets" can generate a "master public key" token which can be used to allow untrusted systems (such as webservers) to generate an unlimited number of addresses without the ability to spend the bitcoins received.

Addresses are often case sensitive and exact

Old-style Bitcoin addresses are case-sensitive. Bitcoin addresses should be copied and pasted using the computer's clipboard wherever possible. If you hand-key a Bitcoin address, and each character is not transcribed exactly - including capitalization - the incorrect address will most likely be rejected by the Bitcoin software. You will have to check your entry and try again.

The probability that a mistyped address is accepted as being valid is 1 in 232, that is, approximately 1 in 4.29 billion.

New-style bech32 addresses are case insensitive.

Proving you receive with an address

Most Bitcoin wallets have a function to "sign" a message, proving the entity receiving funds with an address has agreed to the message. This can be used to, for example, finalise a contract in a cryptographically provable way prior to making payment for it.

Some services will also piggy-back on this capability by dedicating a specific address for authentication only, in which case the address should never be used for actual Bitcoin transactions. When you login to or use their service, you will provide a signature proving you are the same person with the pre-negotiated address.

It is important to note that these signatures only prove one receives with an address. Since Bitcoin transactions do not have a "from" address, you cannot prove you are the sender of funds.

Current standards for message signatures are only compatible with "version zero" bitcoin addresses (that begin with the number 1).

Address validation

If you would like to validate a Bitcoin address in an application, it is advisable to use a method from this thread rather than to just check for string length, allowed characters, or that the address starts with a 1 or 3. Validation may also be done using open source code available in various languages or with an online validating tool.

Multi-signature addresses

Addresses can be created that require a combination of multiple private keys. Since these take advantage of newer features, they begin with the newer prefix of 3 instead of the older 1. These can be thought of as the equivalent of writing a check to two parties - "pay to the order of somebody AND somebody else" - where both parties must endorse the check in order to receive the funds.

The actual requirement (number of private keys needed, their corresponding public keys, etc.) that must be satisfied to spend the funds is decided in advance by the person generating this type of address, and once an address is created, the requirement cannot be changed without generating a new address.

What's in an address

Most Bitcoin addresses are 34 characters. They consist of random digits and uppercase and lowercase letters, with the exception that the uppercase letter "O", uppercase letter "I", lowercase letter "l", and the number "0" are never used to prevent visual ambiguity.

Some Bitcoin addresses can be shorter than 34 characters (as few as 26) and still be valid. A significant percentage of Bitcoin addresses are only 33 characters, and some addresses may be even shorter. Every Bitcoin address stands for a number. These shorter addresses are valid simply because they stand for numbers that happen to start with zeroes, and when the zeroes are omitted, the encoded address gets shorter.

Several of the characters inside a Bitcoin address are used as a checksum so that typographical errors can be automatically found and rejected. The checksum also allows Bitcoin software to confirm that a 33-character (or shorter) address is in fact valid and isn't simply an address with a missing character.

Testnet

Addresses on the Bitcoin Testnet are generated with a different address version, which results in a different prefix. See List of address prefixes and Testnet for more details.

Misconceptions

Address reuse

Addresses are not intended to be used more than once, and doing so has numerous problems associated. See the dedicated article on address reuse for more details.

Address balances

Addresses are not wallets nor accounts, and do not carry balances. They only receive funds, and you do not send "from" an address at any time. Various confusing services and software display bitcoins received with an address, minus bitcoins sent in random unrelated transactions as an "address balance", but this number is not meaningful: it does not imply the recipient of the bitcoins sent to the address has spent them, nor that they still have the bitcoins received.

An example of bitcoin loss resulting from this misunderstanding is when people believed their address contained 3btc. They spent 0.5btc and believed the address now contained 2.5btc when actually it contained zero. The remaining 2.5btc was transferred to a change address which was not backed up and therefore lost. This has happened on a few occasions to users of Paper wallets.

"From" addresses

Bitcoin transactions do not have any kind of origin-, source- or "from" address. See the dedicated article on "from address" for more details.


Address map

Address map.jpg


See Also

References