SPKI

A Simple Public Key Infrastructure implementation (pronounced “spooky”). The structure is defined as

PublicKeyAndChallenge ::= SEQUENCE {
  spki SubjectPublicKeyInfo,
  challenge IA5STRING
}

SignedPublicKeyAndChallenge ::= SEQUENCE {
  publicKeyAndChallenge PublicKeyAndChallenge,
  signatureAlgorithm AlgorithmIdentifier,
  signature BIT STRING
}

where the definitions of SubjectPublicKeyInfo and AlgorithmIdentifier can be found in RFC5280. SPKI is typically used in browsers for generating a public/private key pair and a subsequent certificate request, using the HTML <keygen> element.

Examples

Creating an SPKI

key = OpenSSL::PKey::RSA.new 2048
spki = OpenSSL::Netscape::SPKI.new
spki.challenge = "RandomChallenge"
spki.public_key = key.public_key
spki.sign(key, OpenSSL::Digest::SHA256.new)
#send a request containing this to a server generating a certificate

Verifying an SPKI request

request = #...
spki = OpenSSL::Netscape::SPKI.new request
unless spki.verify(spki.public_key)
  # signature is invalid
end
#proceed