Decrypt the file using public key only

[brijeshgpt7]

I have an encrypted file with pgp extension that needs to be decrypted using the shared public key.
`require 'rubygems'
require 'gpgme'

def passfunc(obj, uid_hint, passphrase_info, prev_was_bad, fd)
io = IO.for_fd(fd, 'w')
io.puts "PASSPHRASE"
io.flush
end

encrypted_data = GPGME::Data.new(File.open("file.xls.pgp"))
key = GPGME::Data.new(File.open("key.txt"))

ctx = GPGME::Ctx.new :passphrase_callback => method(:passfunc)
ctx.import_keys key

decrypted = ctx.decrypt encrypted_data

puts decrypted.read`

Error: r/gems/gpgme-2.0.11/lib/gpgme/ctx.rb:385:in `import_keys': Unsupported protocol (GPGME::Error)

[ueno]

While the error message looks interesting, I don't get what you want to achieve. In public key cryptography, you can't decrypt message with a public key.