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A '''private key''' in the context of Bitcoin is a secret number that allows bitcoins to be spent. Every Bitcoin address has a matching private key, which is saved in the wallet file of the person who owns the balance. The private key is mathematically related to the Bitcoin address, and is designed so that the Bitcoin address can be calculated from the private key, but importantly, the same cannot be done in reverse.
{{sample}}
A '''private key''' in the context of Bitcoin is a secret number that allows bitcoins to be spent.
Every Bitcoin wallet contains one or more private keys, which are saved in the wallet file.
The private keys are mathematically related to all Bitcoin [[address]]es generated for the wallet.


Because the private key is the "ticket" that allows someone to spend bitcoins, it is important that these are kept secure. Private keys can be kept on computer files, but they are also short enough that they can be printed on paper.  An example of a utility that allows extraction of private keys from your wallet file for printing purposes is [[pywallet]].
Because the private key is the "ticket" that allows someone to spend bitcoins, it is important that these are kept secret and safe.
Private keys can be kept on computer files, but are also often [[Seed phrase|written on paper]].


As of March 2012, the easiest way to redeem a private key is on [[MtGox]]'s Add Funds screen.  Funds are deposited to the MtGox account after a six-confirmation wait (typically one hour).  In addition to MtGox, the following services allow redemption of private keys:
Private keys themselves are almost never handled by the user, instead the user will typically be given a [[seed phrase]] that encodes the same information as private keys.


* [[StrongCoin]]
Some wallets allow private keys to be imported without generating any transactions while other wallets or services require that the private key be swept.
When a private key is swept, a transaction is [[Transaction broadcasting|broadcast]] that sends the balance controlled by the private key to a new address in the wallet.
Just as with any other transaction, there is risk of swept transactions to be [[Irreversible Transactions|double-spending]].
 
In contrast, bitcoind provides a facility to import a private key without creating a sweep transaction.
This is considered very dangerous, and not intended to be used even by power users or experts except in very specific cases. Importing keys could lead to the Bitcoins being stolen at any time, from a wallet which has imported an untrusted or otherwise insecure private key - this can include private keys [[Cold storage|generated offline and never seen by someone else]]<ref>[https://bitcoin.stackexchange.com/questions/29948/why-doc-says-importing-private-keys-is-so-dangerous Bitcoin StackExchange - Why doc says importing private keys is so dangerous?]</ref><ref>[https://bitcoin.stackexchange.com/questions/18619/why-so-many-warnings-about-importing-private-keys Bitcoin StackExchange - Why so many warnings about importing private keys?]</ref>.


==An example private key==
==An example private key==
In Bitcoin, a private key is a 256-bit number, which can be represented one of several ways. Here is a private key in hexadecimal - 256 bits in hexadecimal is 32 bytes, or 64 characters in the range 0-9 or A-F.
In Bitcoin, a private key is a 256-bit number, which can be represented one of several ways.
Here is a private key in hexadecimal - 256 bits in hexadecimal is 32 bytes, or 64 characters in the range 0-9 or A-F.


  E9 87 3D 79 C6 D8 7D C0 FB 6A 57 78 63 33 89 F4 45 32 13 30 3D A6 1F 20 BD 67 FC 23 3A A3 32 62
  E9873D79C6D87DC0FB6A5778633389{{taggant private key}}F4453213303DA61F20BD67FC233AA33262


==Range of valid private keys==
==Range of valid ECDSA private keys==
Nearly every 256-bit number is a valid private key.  Specifically, any 256-bit number between 0x1 and 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFEBAAEDCE6AF48A03BBFD25E8CD0364141 is a valid private key.
Nearly every 256-bit number is a valid [[ECDSA]] private key.  Specifically, any 256-bit number from 0x1 to 0xFFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFE BAAE DCE6 AF48 A03B BFD2 5E8C D036 4140 is a valid private key.


The range of valid private keys is governed by the [[secp256k1]] ECDSA standard used by Bitcoin.
The range of valid private keys is governed by the [[secp256k1]] ECDSA standard used by Bitcoin.


==Base 58 Wallet Import format==
==Hierarchical Deterministic (HD) Wallet Keys==
When we represent private keys in Bitcoin, however, we use a shorter format known as [[wallet import format]], which offers a few advantages.  The wallet import format is shorter, and includes built-in error checking codes so that typos can be automatically detected and/or corrected (which is impossible in hex format).  Wallet import format is the most common way to represent private keys in Bitcoin.  For private keys associated with uncompressed public keys, they are 51 characters and always start with the number 5. Private keys associated with compressed public keys are 52 characters and start with a capital L or K. This is the same private key in wallet import format.
{{main|Hierarchical deterministic wallet}}


  5Kb8kLf9zgWQnogidDA76MzPL6TsZZY36hWXMssSzNydYXYB9KF
Wallet software may use a [[BIP 0032|BIP 32]] seed to generate many private keys and corresponding public keys from a single secret value. This is called a ''hierarchical deterministic wallet'', or ''HD wallet'' for short.  The seed value, or ''master extended key'', consists of a 256-bit private key and a 256-bit ''chain code'', for 512 bits in total.  The seed value should not be confused with the private keys used directly to sign Bitcoin transactions.


When a private key is imported, it always corresponds to exactly one [[Address|Bitcoin address]].  Any utility which performs the conversion can display the matching Bitcoin address.  The mathematical conversion is somewhat complex and best left to a computer, but it's notable that each private key will always correspond to the same address no matter which program is used to convert it.
Users are strongly advised to use HD wallets, for safety reasons:  An HD wallet only needs to be backed up once typically using a [[seed phrase]]; thereafter in the future, that single backup can always deterministically regenerate the same private keys.  Therefore, it can safely recover all addresses, and all funds sent to those addresses.  Non-HD wallets generate a new randomly-selected private key for each new address; therefore, if the wallet file is lost or damaged, the user will irretrievably lose all funds received to addresses generated after the most recent backup.


The Bitcoin address corresponding to the sample above is: 1CC3X2gu58d6wXUWMffpuzN9JAfTUWu4Kj
==Base58 Wallet Import format==
{{main|Wallet import format}}
When importing or sweeping ECDSA private keys, a shorter format known as [[wallet import format]] is often used, which offers a few advantages.
The wallet import format is shorter, and includes built-in error checking codes so that typos can be automatically detected and/or corrected (which is impossible in hex format) and type bits indicating how it is intended to be used.
Wallet import format is the most common way to represent private keys in Bitcoin.
For private keys associated with uncompressed public keys, they are 51 characters and always start with the number 5 on mainnet (9 on testnet). Private keys associated with compressed public keys are 52 characters and start with a capital L or K on mainnet (c on testnet). This is the same private key in (mainnet) wallet import format:
 
5Kb8kLf9zgWQnogidDA76Mz{{taggant private key}}PL6TsZZY36hWXMssSzNydYXYB9KF
 
When a WIF private key is imported, it always corresponds to exactly one [[Address|Bitcoin address]].
Any utility which performs the conversion can display the matching Bitcoin address.
The mathematical conversion is somewhat complex and best left to a computer, but it's notable that the WIF guarantees it will always correspond to the same address no matter which program is used to convert it.
 
The Bitcoin address implemented using the sample above is: 1CC3X2gu58d6wXUW{{taggant address}}MffpuzN9JAfTUWu4Kj


==Mini private key format==
==Mini private key format==
{{main|Mini private key format}}
Some applications use the [[mini private key format]].  Not every private key or Bitcoin address has a corresponding mini private key - they have to be generated a certain way in order to ensure a mini private key exists for an address.  The mini private key is used for applications where space is critical, such as in QR codes and in [[physical bitcoins]].  The above example has a mini key, which is:
Some applications use the [[mini private key format]].  Not every private key or Bitcoin address has a corresponding mini private key - they have to be generated a certain way in order to ensure a mini private key exists for an address.  The mini private key is used for applications where space is critical, such as in QR codes and in [[physical bitcoins]].  The above example has a mini key, which is:


  SzavMBLoXU6kDrqtUVmffv
  SzavMBLoXU6{{taggant private key}}kDrqtUVmffv


==Summary==
==Summary==
Any Bitcoins sent to the address 1CC3X2gu58d6wXUWMffpuzN9JAfTUWu4Kj can be spent by anybody who knows the private key in ''any'' of the three formats.  That includes bitcoins presently at the address, as well as any bitcoins that are ever sent to it in the future. The private key is only needed to spend the balance, not necessarily to see it. The Bitcoin balance of the address can be determined by anybody with the public [[Block Explorer]] at http://www.blockexplorer.com/address/1CC3X2gu58d6wXUWMffpuzN9JAfTUWu4Kj - even if they don't have the private key.
Any Bitcoins sent to the address 1CC3X2gu58d6wXUW{{taggant address}}MffpuzN9JAfTUWu4Kj can be spent by anybody who knows the private key implementing it in ''any'' of the three formats, regardless of when the bitcoins were sent, unless the wallet receiving them has since made use of the coins generated.
The private key is only needed to spend the bitcoins, not necessarily to see the value of them.
 
If a private key controlling unspent bitcoins is compromised or stolen, the value can only be protected if it is immediately spent to a different output which is secure.
Because bitcoins can only be spent once, when they are spent using a private key, the private key becomes worthless.
It is often possible, but inadvisable and insecure, to use the address implemented by the private key again, in which case the same private key would be [[Address reuse|reused]].
 
==See Also==
 
* [[Paper wallet]]
* [[How to import private keys]]
* [[How to import private keys v7+]]
 
==References==
<references />
 
[[es:Clave privada]]


If a private key with a Bitcoin balance is compromised or stolen, the bitcoin balance can only be protected if it is immediately spent to a different address whose private key is not compromised.  Because bitcoins can only be spent once, when they are spent away from a private key, the private key is worthless unless more coins are sent to the address.
[[Category:Technical]]

Latest revision as of 14:14, 4 May 2019

This page contains sample addresses and/or private keys. Do not send bitcoins to or import any sample keys; you will lose your money.

A private key in the context of Bitcoin is a secret number that allows bitcoins to be spent. Every Bitcoin wallet contains one or more private keys, which are saved in the wallet file. The private keys are mathematically related to all Bitcoin addresses generated for the wallet.

Because the private key is the "ticket" that allows someone to spend bitcoins, it is important that these are kept secret and safe. Private keys can be kept on computer files, but are also often written on paper.

Private keys themselves are almost never handled by the user, instead the user will typically be given a seed phrase that encodes the same information as private keys.

Some wallets allow private keys to be imported without generating any transactions while other wallets or services require that the private key be swept. When a private key is swept, a transaction is broadcast that sends the balance controlled by the private key to a new address in the wallet. Just as with any other transaction, there is risk of swept transactions to be double-spending.

In contrast, bitcoind provides a facility to import a private key without creating a sweep transaction. This is considered very dangerous, and not intended to be used even by power users or experts except in very specific cases. Importing keys could lead to the Bitcoins being stolen at any time, from a wallet which has imported an untrusted or otherwise insecure private key - this can include private keys generated offline and never seen by someone else[1][2].

An example private key

In Bitcoin, a private key is a 256-bit number, which can be represented one of several ways. Here is a private key in hexadecimal - 256 bits in hexadecimal is 32 bytes, or 64 characters in the range 0-9 or A-F. 

E9873D79C6D87DC0FB6A5778633389_SAMPLE_PRIVATE_KEY_DO_NOT_IMPORT_F4453213303DA61F20BD67FC233AA33262

Range of valid ECDSA private keys

Nearly every 256-bit number is a valid ECDSA private key. Specifically, any 256-bit number from 0x1 to 0xFFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFE BAAE DCE6 AF48 A03B BFD2 5E8C D036 4140 is a valid private key.

The range of valid private keys is governed by the secp256k1 ECDSA standard used by Bitcoin.

Hierarchical Deterministic (HD) Wallet Keys

Main article: Hierarchical deterministic wallet

Wallet software may use a BIP 32 seed to generate many private keys and corresponding public keys from a single secret value. This is called a hierarchical deterministic wallet, or HD wallet for short. The seed value, or master extended key, consists of a 256-bit private key and a 256-bit chain code, for 512 bits in total. The seed value should not be confused with the private keys used directly to sign Bitcoin transactions.

Users are strongly advised to use HD wallets, for safety reasons: An HD wallet only needs to be backed up once typically using a seed phrase; thereafter in the future, that single backup can always deterministically regenerate the same private keys. Therefore, it can safely recover all addresses, and all funds sent to those addresses. Non-HD wallets generate a new randomly-selected private key for each new address; therefore, if the wallet file is lost or damaged, the user will irretrievably lose all funds received to addresses generated after the most recent backup.

Base58 Wallet Import format

Main article: Wallet import format

When importing or sweeping ECDSA private keys, a shorter format known as wallet import format is often used, which offers a few advantages. The wallet import format is shorter, and includes built-in error checking codes so that typos can be automatically detected and/or corrected (which is impossible in hex format) and type bits indicating how it is intended to be used. Wallet import format is the most common way to represent private keys in Bitcoin. For private keys associated with uncompressed public keys, they are 51 characters and always start with the number 5 on mainnet (9 on testnet). Private keys associated with compressed public keys are 52 characters and start with a capital L or K on mainnet (c on testnet). This is the same private key in (mainnet) wallet import format: 

5Kb8kLf9zgWQnogidDA76Mz_SAMPLE_PRIVATE_KEY_DO_NOT_IMPORT_PL6TsZZY36hWXMssSzNydYXYB9KF

When a WIF private key is imported, it always corresponds to exactly one Bitcoin address. Any utility which performs the conversion can display the matching Bitcoin address. The mathematical conversion is somewhat complex and best left to a computer, but it's notable that the WIF guarantees it will always correspond to the same address no matter which program is used to convert it.

The Bitcoin address implemented using the sample above is: 1CC3X2gu58d6wXUW_SAMPLE_ADDRESS_DO_NOT_SEND_MffpuzN9JAfTUWu4Kj

Mini private key format

Main article: Mini private key format

Some applications use the mini private key format. Not every private key or Bitcoin address has a corresponding mini private key - they have to be generated a certain way in order to ensure a mini private key exists for an address. The mini private key is used for applications where space is critical, such as in QR codes and in physical bitcoins. The above example has a mini key, which is: 

SzavMBLoXU6_SAMPLE_PRIVATE_KEY_DO_NOT_IMPORT_kDrqtUVmffv

Summary

Any Bitcoins sent to the address 1CC3X2gu58d6wXUW_SAMPLE_ADDRESS_DO_NOT_SEND_MffpuzN9JAfTUWu4Kj can be spent by anybody who knows the private key implementing it in any of the three formats, regardless of when the bitcoins were sent, unless the wallet receiving them has since made use of the coins generated. The private key is only needed to spend the bitcoins, not necessarily to see the value of them.

If a private key controlling unspent bitcoins is compromised or stolen, the value can only be protected if it is immediately spent to a different output which is secure. Because bitcoins can only be spent once, when they are spent using a private key, the private key becomes worthless. It is often possible, but inadvisable and insecure, to use the address implemented by the private key again, in which case the same private key would be reused.

See Also

References

  1. ↑ Bitcoin StackExchange - Why doc says importing private keys is so dangerous?
  2. ↑ Bitcoin StackExchange - Why so many warnings about importing private keys?
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