IF: Generate bls key pair

[linh2931]

Resolves #1525

Add leap-util subcommands to create key pairs and pop (proof of possession), and tests.

Help looks like

./leap-util bls create --help-all
Create various items
Usage: bin/leap-util bls create [OPTIONS] SUBCOMMAND

Options:
  -h,--help              Print this help message and exit
  --help-all             Show all help


Subcommands:
├  key                    Create a new keypair and print the public and private keys
│
└  pop                    Create proof of possession for the corresponding public key of a given private key

./leap-util bls create key --help-all
Create a new keypair and print the public and private keys
Usage: bin/leap-util bls create key [OPTIONS]

Options:
  -h,--help              Print this help message and exit
  --help-all             Show all help
  -f,--file TEXT         Name of file to write private/public key output to. (Must be set, unless "--to-console" is passed
  --to-console           Print private/public keys to console.

./leap-util bls create pop --help-all
Create proof of possession for the corresponding public key of a given private key
Usage: bin/leap-util bls create pop [OPTIONS]

Options:
  -h,--help              Print this help message and exit
  --help-all             Show all help
  -f,--file TEXT         Name of file storing the private key. (one and only one of "-f,--file" and "--private-key" must be set)
  --private-key TEXT     The private key. (one and only one of "-f,--file" and "--private-key" must be set)

Create key pair looks like

./leap-util bls create key --to-console
Private key: PVT_BLS_qTV8Td/8NUuPzBvEkO3ofEA5nCyFdBHxv50H9GACHUCY6hXw
Public key: PUB_BLS_laqiihyNRuivOF5QLo6lC20nKm5XdC87gEOtvsAnPtDd4TeaOHqF3hqPa0XOUFg+/BfRNg==
Proof of Possession: SIG_BLS_lrd6xlmZFPdBcx6sEAErBeivkDTrxdiwyeCUbiU/q8JMVErkCSCNBbW5YCJnkblwEWAklvYHbVoZ0OUHpB8jkkYz35qoe1+rvjsvNAv9nS2tQqmhtBXOWsyLPNL7RLPO2gDojw==

Create pop looks like

./leap-util bls create pop --private-key PVT_BLS_qTV8Td/8NUuPzBvEkO3ofEA5nCyFdBHxv50H9GACHUCY6hXw
Proof of Possession: SIG_BLS_lrd6xlmZFPdBcx6sEAErBeivkDTrxdiwyeCUbiU/q8JMVErkCSCNBbW5YCJnkblwEWAklvYHbVoZ0OUHpB8jkkYz35qoe1+rvjsvNAv9nS2tQqmhtBXOWsyLPNL7RLPO2gDojw==
Public key: PUB_BLS_laqiihyNRuivOF5QLo6lC20nKm5XdC87gEOtvsAnPtDd4TeaOHqF3hqPa0XOUFg+/BfRNg==

[fcecin]

\"-f, --file\" (add -f to the message)

[linh2931]

Thanks!

[fcecin]

\"-f, --file\" (add -f to the message)

[ericpassmore]

Note:start
group: IF
category: CRYPTO
summary: ./leap-util bls create pop new leap util command to generate proof of possession keys. Generated keys are BLS keys in raw, affine form.
Note:end