How can I convert my private key from bitaddress.org to WIF without putting the key into a website or a programme? Rule number 1 says: don't put your private key into any website or programme, unless you're performing a transfer. This way you won't be robbed.
Then, I want to &quot;sweep&quot; my money off a paper wallet from bitaddress.org, but Electrum wants me to put the private key in WIF format ( https://bitcoinelectrum.com/sweeping-your-private-keys-into-electrum/ ). How can I convert my key to WIF without breaking the rule number 1?
By the way, what's the name of the format bitaddress.org returns private keys in? It is base58?
bitaddress.org already provides your private key in Wallet Import Format, which is encoded in base58check format.
In the example screenshot below, the base58check-encoded WIF private key is KzNKqwBPaVehsA2F94n9UJ5mrkM9NazBjqBBwsb2U9pAGLdc4md3
To address your &quot;rule 1&quot;, the most secure way to handle this data is load Electrum onto an airgapped machine, enter the private key into that secure computer, and then use it to sign a transaction you build with an &quot;online&quot; machine that has access to the UTXO set and your wallet address.

Warning: Do not use the key or address in this example for any reason at all besides looking at it and learning! Pasting private keys on websites is always a terrible idea.