Es muy sencillo convertir una clave pública codificada en formato base 64 como la siguiente a un formato binario:
-----BEGIN PGP PUBLIC KEY BLOCK-----
mQENBFsqQKkBCAC0vf9djXYQYQNfKN2ljM8BAjuRJ5GlJMt7rQBdCgFOqjyv2EaG
pZImK07jtGWSDa0eat2qGRVwKynUoh8WQOy+fKE1yq2rlOpiV6wMj4vTB+2tX5pe
sBT4sVpcAWwZehJTyBSMMntmeJQl//GBF8HLB1eomeNfe9WNR4zLC2e5JlCIDUmj
NjPZndvq+AwEvFhzwXopSD8bcktq0IG+m3EWzAy2TvAWvNE+3lhJxfEXxJ6t5xUi
GQm2L1Eni3CefGbuATh8DuTOdDlNw4igzvsjEPi4n5wKJZ/HR1zvj7Qj/PSUiEw+
R2FtXPdeka7CWhhA044DdsQANM7dXyy68BrRABEBAAG0LHJlcHJlcHJvIDxyZXBy
ZXByb0BpbnN0aXR1dG8uZXh0cmVtYWR1cmEuZXM+iQFOBBMBCAA4AhsDBQsJCAcC
BhUICQoLAgQWAgMBAh4BAheAFiEEf0/mWrq1LfofBJMoJcYI+0eloLMFAl7uLiMA
CgkQJcYI+0eloLMlIQgAk1oILsltFC7boO7tYCKafDEZ1j4G3CTIeoTX2CMbsGjg
wP/G1H0nOX5+bGv6cts7RUrnSMueBzh43y/4OsQw/VH/FcuJtjBQkpf/DTg02RGu
8YQ7KV7Kd8nStHOHFRSJWTwoQql6h9bzXGxKbyD5NTtj1yk730HGd42WH/YTbYT6
g5iYw7Ik69nYOGwWvpxAa682D7mrY4R4GB0QcDkOPbNXpaux1PfqZtJsCmfRGAVc
32Do0SIwPuqLDUxBBpj/4UWbQEekLy8wSLkGKZ4ad/8Y5Aw5NSuV5AbiIWlM0h2d
vMC/k1DVydOxvE+VCTm8jTQcLVwoIsOpBiwrpziQDrkBDQRbKkCpAQgAvTzTvq4E
TB5w8j73tRs5m4V74PMmapmPnNZ6h2y78VrtNW4BOOqwL11+x2uwiNHrivHRnQRG
7FXI5THCTBg63OH2hlqjQGImoHang4Pb/Q5ENykM1gcwX+HlafbK7LZ1PnAl/bYL
4AnCTkTq7k+UHw0T+5+K64U1+lU6lSLU0SFAD/G+WVw7Mszzr7PDUhrjiRkoVMBS
FFHSXJrNFuNBihHg0Wmf8hzd7FAZ4U0LqGZXXNmTQT/7+5pwTfSgHVhsJqbP0OaR
WwTo+kipBVDY3YetUuOF3kKGATGBoN//oYG2rkxqWc+2CzwgJkW/M0oF5vVDWgHy
GvWbbc5tM617NwARAQABiQE8BBgBCAAmFiEEf0/mWrq1LfofBJMoJcYI+0eloLMF
AlsqQKkCGwwFCQPCZwAACgkQJcYI+0eloLNJ8wgAoKTLcanAZ8TEILj9trFIjqNv
U7qi5MS++SN1oLGM80ipI5zZsCaLDXOxe8Q2GS6wTnnBgJXU1Cr1Qw8FFcbjqDAK
xl7GYUnIiwl1quy/+GWKywi0dCXmFJgAwfCFjKookEhV1ime2aePp82jRc502AZp
g3vnYmdFDO1rjwLN8s6McrrmhVGRsU1sQdqrbv2AF/0+HCfWK51vobOM8HA3s23D
4F/iC6eRaNv90SvIWw8ArWJ6PU2HEbP2A2QCG4pPfH97VHzfJyUXiAtXmUxoIxv8
pUcFmY15XQFPPiZ9sHkJIceqG0XCw57l07SJk0D1EKc7GeMWZeiEimtPjhiBRg==
=BiyL
-----END PGP PUBLIC KEY BLOCK-----
Suponiendo que tenemos un fichero key.asc con el formato anterior que queremos convertir a binario, podemos usar el comando gpg:
gpg -o key.gpg --dearmor key.asc