Bitcoin/address validation: Difference between revisions
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{{draft task}}
Write a program that takes a [[wp:bitcoin|bitcoin address]] as argument, and checks whether or not this address is
A bitcoin address uses a base58 encoding, which uses an alphabet of the characters 0 .. 9, A ..Z, a .. z, but without the four characters 0, O, I and l.
With this encoding, a bitcoin address encodes
* the first byte is the version number, which will be zero for this task ;
* the next twenty bytes are a [[RIPEMD-160]] digest, but you don't have to know that for this task: you can consider them a pure arbitrary data ;
* the last four bytes are a checksum check. They are the first four bytes of a double [[SHA-256]] digest of the previous 21 bytes.
To check the bitcoin address, you must read the first twenty-one bytes, compute the checksum, and check that it corresponds to the last four bytes.
The program can either return a boolean value or throw an exception when not valid.
You can use a digest library for [[SHA-256]].
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