key decoder

#!/usr/bin/env ruby

require "base64"
require "openssl"

# For private key:
# version           Version,
# modulus           INTEGER,  -- n
# publicExponent    INTEGER,  -- e
# privateExponent   INTEGER,  -- d
# prime1            INTEGER,  -- p
# prime2            INTEGER,  -- q
# exponent1         INTEGER,  -- d mod (p-1)
# exponent2         INTEGER,  -- d mod (q-1)
# coefficient       INTEGER,  -- (inverse of q) mod p
#
# where n=pq, d=(inverse of e) mod n

# For public key:
# modulus           INTEGER,  -- n
# publicExponent    INTEGER,  -- e

def print_asn(d, prefix="")
  case d
  when OpenSSL::ASN1::Sequence
    puts "#{prefix}Sequence:"
    d.value.each do |item|
      print_asn item, "#{prefix}  "
    end
  when OpenSSL::ASN1::Integer
    puts "#{prefix}#{d.value}"
  else
    raise
  end
end

data = STDIN.read
data = Base64.decode64(data)

print_asn OpenSSL::ASN1.decode(data)