Wallet Import Format (WIF)

Wallet Import Format (WIF, also known as Wallet Export Format) is a way of encoding a private ECDSA key to make it easier to copy.

A testing suite is available for encoding and decoding of WIF at:

http://gobittest.appspot.com/PrivateKey

Private key to WIF

1 - Take a private key

   0C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D

2 - Add a 0x80 byte in front of it for mainnet addresses or 0xef for testnet addresses. Also add a 0x01 byte at the end if the private key will correspond to a compressed public key

   800C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D

3 - Perform SHA-256 hash on the extended key

   8147786C4D15106333BF278D71DADAF1079EF2D2440A4DDE37D747DED5403592

4 - Perform SHA-256 hash on result of SHA-256 hash

   507A5B8DFED0FC6FE8801743720CEDEC06AA5C6FCA72B07C49964492FB98A714

5 - Take the first 4 bytes of the second SHA-256 hash, this is the checksum

   507A5B8D

6 - Add the 4 checksum bytes from point 5 at the end of the extended key from point 2

   800C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D507A5B8D

7 - Convert the result from a byte string into a base58 string using Base58Check encoding. This is the Wallet Import Format

   5HueCGU8rMjxEXxiPuD5BDku4MkFqeZyd4dZ1jvhTVqvbTLvyTJ

WIF to private key

1 - Take a Wallet Import Format string

   5HueCGU8rMjxEXxiPuD5BDku4MkFqeZyd4dZ1jvhTVqvbTLvyTJ

2 - Convert it to a byte string using Base58Check encoding

   800C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D507A5B8D

3 - Drop the last 4 checksum bytes from the byte string

   800C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D

4 - Drop the first byte (it should be 0x80). If the private key corresponded to a compressed public key, also drop the last byte (it should be 0x01). If it corresponded to a compressed public key, the WIF string will have started with K or L instead of 5 (or c instead of 9 on testnet). This is the private key.

   0C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D

WIF checksum checking

1 - Take the Wallet Import Format string

   5HueCGU8rMjxEXxiPuD5BDku4MkFqeZyd4dZ1jvhTVqvbTLvyTJ

2 - Convert it to a byte string using Base58Check encoding

   800C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D507A5B8D

3 - Drop the last 4 checksum bytes from the byte string

   800C28FCA386C7A227600B2FE50B7CAE11EC86D3BF1FBE471BE89827E19D72AA1D

3 - Perform SHA-256 hash on the shortened string

   8147786C4D15106333BF278D71DADAF1079EF2D2440A4DDE37D747DED5403592

4 - Perform SHA-256 hash on result of SHA-256 hash

   507A5B8DFED0FC6FE8801743720CEDEC06AA5C6FCA72B07C49964492FB98A714

5 - Take the first 4 bytes of the second SHA-256 hash, this is the checksum

   507A5B8D

6 - Make sure it is the same, as the last 4 bytes from point 2

   507A5B8D

7 - If they are, and the byte string from point 2 starts with 0x80 (0xef for testnet addresses), then there is no error.