I was browsing through blockchain today and I noticed new - weird looking adresses like this bc1qdl753ur9ucwa3cgfrud2nqvu7k69dykk3cwwx6g64a5szn3xw92sp8mc7a.
What block explorer was showing these?
What type are these???
These addresses are bech32 addresses. They are for the native segwit output type. They are specified in
BIP 173How would you create transactions with those?
As you would with any other type of address. The wallet software will handle it for you. If the wallet software supports bech32 addresses, it will know how to decode them and create transactions with them. These addresses specifically tell the wallet what type segwit output to create.
They are some sort of witness adresses?
Yes.
Each address has a private key, the ones start with 3 have 2/3 private keys, what type of a private key would have this one?
It depends.
First of all, addresses starting with a 3 do not necessarily have private keys associated with them, and not necessarily 2 or 3 private keys. Addresses starting with a 3 are P2SH addresses which means they have a script associated with them, and that script can be whatever you want so long as it is a valid script. This means that it can contain many public keys (and thus have many private keys) or no public keys (and thus be associated with no private keys).
bech32 addresses are for the P2WPKH and P2WSH output types. For P2WPKH, there is one private key. P2WSH is like P2SH; it is associated with an arbitrary script.
Also, there are no types of private keys. All private keys are the same "type"': a 256 bit integer.
Are they more secure?
How do you define "more secure"?
Bech32 addresses have built in error detection and correction (they can correct, but software should not be automatically correcting errors). I don't think they are any more or less secure than "normal" addresses.
