Specify whether an imported key should be imported as compressed or uncompressed #2699

At the moment the call to import a private key looks like:

importprivkey <bitcoinprivkey> [label] [rescan=true]

I would like to expand it with an optional parameter of [compressed=true]. The reasoning behind it is that some people want to import their keys in a specific format to conform with either their previous format (keeping the same address between BitcoinQT and their other wallet that may or may not use compressed format), or maps to a specific vanity address they desire. The adoption of this option would encourage other wallet hosts and developers to do the same and encourage more people to use compressed keys (as opposed to uncompressed keys which are the norm at the moment since everyone else is using them).

I'm pretty sure the private key encoding specifies whether it's compressed or not...

I think that's public key encoding. The same private key can be mapped to both compressed and uncompressed public key. It is different from Wallet Import Format (which is private key + checksum) or Mini Private Key (which needs to be hashed into a normal private key).

Reading base58.h, it seems that the private key format simply appends a 0x01 byte to the binary data, if it's a compressed key, before running it through the usual Base58Check algorithm...

@luke-jr is correct. If the length of the key is 33, and the last byte of the private key is 0x01, the key is interpreted as compressed. Otherwise, it is treated as uncompressed. So an additional parameter is not needed.