diff --git a/README.md b/README.md
index eace9f5..91cedbc 100644
--- a/README.md
+++ b/README.md
@@ -14,11 +14,11 @@ gem install ssh_data
 require "ssh_data"
 
 key_data = File.read("~/.ssh/id_rsa.pub")
-key = SSHData::PublicKey.parse(key_data)
+key = SSHData::PublicKey.parse_openssh(key_data)
 #=> <SSHData::PublicKey::RSA>
 
 cert_data = = File.read("~/.ssh/id_rsa-cert.pub")
-cert = SSHData::Certificate.parse(cert_data)
+cert = SSHData::Certificate.parse_openssh(cert_data)
 #=> <SSHData::PublicKey::Certificate>
 
 cert.key_id
diff --git a/lib/ssh_data.rb b/lib/ssh_data.rb
index ad69858..0097a63 100644
--- a/lib/ssh_data.rb
+++ b/lib/ssh_data.rb
@@ -2,15 +2,16 @@
 require "base64"
 
 module SSHData
-  # Break down a public key or certificate into its algorith, raw key, and host.
+  # Break down a key in OpenSSH authorized_keys format (see sshd(8) manual
+  # page).
   #
-  # key - An SSH formatted public key or certificate, including algo, encoded
-  #       key and optional user/host names.
+  # key - An OpenSSH formatted public key or certificate, including algo,
+  #       base64 encoded key and optional comment.
   #
   # Returns an Array containing the algorithm String , the raw key or
-  # certificate String and the host String or nil.
+  # certificate String and the comment String or nil.
   def key_parts(key)
-    algo, b64, host = key.strip.split(" ", 3)
+    algo, b64, comment = key.strip.split(" ", 3)
     if algo.nil? || b64.nil?
       raise DecodeError, "bad data format"
     end
@@ -21,7 +22,7 @@ def key_parts(key)
       raise DecodeError, "bad data format"
     end
 
-    [algo, raw, host]
+    [algo, raw, comment]
   end
 
   extend self
diff --git a/lib/ssh_data/certificate.rb b/lib/ssh_data/certificate.rb
index e07a594..97ef2a4 100644
--- a/lib/ssh_data/certificate.rb
+++ b/lib/ssh_data/certificate.rb
@@ -12,21 +12,27 @@ class Certificate
     ALGO_ECDSA521 = "ecdsa-sha2-nistp521-cert-v01@openssh.com"
     ALGO_ED25519  = "ssh-ed25519-cert-v01@openssh.com"
 
+    ALGOS = [
+      ALGO_RSA, ALGO_DSA, ALGO_ECDSA256, ALGO_ECDSA384, ALGO_ECDSA521,
+      ALGO_ED25519
+    ]
+
     attr_reader :algo, :nonce, :public_key, :serial, :type, :key_id,
                 :valid_principals, :valid_after, :valid_before,
                 :critical_options, :extensions, :reserved, :ca_key, :signature
 
-    # Parse an SSH certificate.
+    # Parse an OpenSSH certificate in authorized_keys format (see sshd(8) manual
+    # page).
     #
-    # cert              - An SSH formatted certificate, including key algo,
-    #                     encoded key and optional user/host names.
+    # cert              - An OpenSSH formatted certificate, including key algo,
+    #                     base64 encoded key and optional comment.
     # unsafe_no_verify: - Bool of whether to skip verifying certificate signature
     #                     (Default false)
     #
     # Returns a Certificate instance.
-    def self.parse(cert, unsafe_no_verify: false)
+    def self.parse_openssh(cert, unsafe_no_verify: false)
       algo, raw, _ = SSHData.key_parts(cert)
-      parsed = parse_raw(raw, unsafe_no_verify: unsafe_no_verify)
+      parsed = parse_rfc4253(raw, unsafe_no_verify: unsafe_no_verify)
 
       if parsed.algo != algo
         raise DecodeError, "algo mismatch: #{parsed.algo.inspect}!=#{algo.inspect}"
@@ -35,14 +41,17 @@ def self.parse(cert, unsafe_no_verify: false)
       parsed
     end
 
-    # Parse an SSH certificate.
+    # Deprecated
+    singleton_class.send(:alias_method, :parse, :parse_openssh)
+
+    # Parse an RFC 4253 binary SSH certificate.
     #
-    # cert              - A raw binary certificate String.
+    # cert              - A RFC 4253 binary certificate String.
     # unsafe_no_verify: - Bool of whether to skip verifying certificate
     #                     signature (Default false)
     #
     # Returns a Certificate instance.
-    def self.parse_raw(raw, unsafe_no_verify: false)
+    def self.parse_rfc4253(raw, unsafe_no_verify: false)
       data, read = Encoding.decode_certificate(raw)
 
       if read != raw.bytesize
diff --git a/lib/ssh_data/private_key.rb b/lib/ssh_data/private_key.rb
index 934599e..af90836 100644
--- a/lib/ssh_data/private_key.rb
+++ b/lib/ssh_data/private_key.rb
@@ -8,7 +8,7 @@ module PrivateKey
 
     # Parse an SSH private key.
     #
-    # key - An PEM encoded OpenSSH private key.
+    # key - A PEM or OpenSSH encoded private key.
     #
     # Returns an Array of PrivateKey::Base subclass instances.
     def self.parse(key)
@@ -31,6 +31,11 @@ def self.parse(key)
       raise DecodeError, "bad private key. maybe encrypted?"
     end
 
+    # Parse an OpenSSH formatted private key.
+    #
+    # key - An OpenSSH encoded private key.
+    #
+    # Returns an Array of PrivateKey::Base subclass instances.
     def self.parse_openssh(key)
       raw = Encoding.decode_pem(key, OPENSSH_PEM_TYPE)
 
diff --git a/lib/ssh_data/public_key.rb b/lib/ssh_data/public_key.rb
index fb509e8..56f89cf 100644
--- a/lib/ssh_data/public_key.rb
+++ b/lib/ssh_data/public_key.rb
@@ -8,15 +8,21 @@ module PublicKey
     ALGO_ECDSA521 = "ecdsa-sha2-nistp521"
     ALGO_ED25519  = "ssh-ed25519"
 
-    # Parse an SSH public key.
+    ALGOS = [
+      ALGO_RSA, ALGO_DSA, ALGO_ECDSA256, ALGO_ECDSA384, ALGO_ECDSA521,
+      ALGO_ED25519
+    ]
+
+    # Parse an OpenSSH public key in authorized_keys format (see sshd(8) manual
+    # page).
     #
-    # key - An SSH formatted public key, including algo, encoded key and optional
-    #       user/host names.
+    # key - An OpenSSH formatted public key, including algo, base64 encoded key
+    #       and optional comment.
     #
     # Returns a PublicKey::Base subclass instance.
-    def self.parse(key)
+    def self.parse_openssh(key)
       algo, raw, _ = SSHData.key_parts(key)
-      parsed = parse_raw(raw)
+      parsed = parse_rfc4253(raw)
 
       if parsed.algo != algo
         raise DecodeError, "algo mismatch: #{parsed.algo.inspect}!=#{algo.inspect}"
@@ -25,12 +31,15 @@ def self.parse(key)
       parsed
     end
 
-    # Parse an SSH public key.
+    # Deprecated
+    singleton_class.send(:alias_method, :parse, :parse_openssh)
+
+    # Parse an RFC 4253 binary SSH public key.
     #
-    # key - A raw binary public key String.
+    # key - A RFC 4253 binary public key String.
     #
     # Returns a PublicKey::Base subclass instance.
-    def self.parse_raw(raw)
+    def self.parse_rfc4253(raw)
       data, read = Encoding.decode_public_key(raw)
 
       if read != raw.bytesize
diff --git a/lib/ssh_data/public_key/base.rb b/lib/ssh_data/public_key/base.rb
index 7b2f63c..ce16e43 100644
--- a/lib/ssh_data/public_key/base.rb
+++ b/lib/ssh_data/public_key/base.rb
@@ -40,6 +40,15 @@ def raw
         raise "implement me"
       end
 
+      # OpenSSH public key in authorized_keys format (see sshd(8) manual page).
+      #
+      # comment - Optional String comment to append.
+      #
+      # Returns a String key.
+      def openssh(comment: nil)
+        [algo, Base64.strict_encode64(raw), comment].compact.join(" ")
+      end
+
       # Is this public key equal to another public key?
       #
       # other - Another SSHData::PublicKey::Base instance to compare with.
diff --git a/spec/certificate_spec.rb b/spec/certificate_spec.rb
index c6f4f2d..c2fc29a 100644
--- a/spec/certificate_spec.rb
+++ b/spec/certificate_spec.rb
@@ -1,60 +1,66 @@
 require_relative "./spec_helper"
 
 describe SSHData::Certificate do
-  let(:rsa_cert)     { described_class.parse(fixture("rsa_leaf_for_rsa_ca-cert.pub")) }
-  let(:dsa_cert)     { described_class.parse(fixture("dsa_leaf_for_rsa_ca-cert.pub")) }
-  let(:ecdsa_cert)   { described_class.parse(fixture("ecdsa_leaf_for_rsa_ca-cert.pub")) }
-  let(:ed25519_cert) { described_class.parse(fixture("ed25519_leaf_for_rsa_ca-cert.pub")) }
+  let(:rsa_cert)     { described_class.parse_openssh(fixture("rsa_leaf_for_rsa_ca-cert.pub")) }
+  let(:dsa_cert)     { described_class.parse_openssh(fixture("dsa_leaf_for_rsa_ca-cert.pub")) }
+  let(:ecdsa_cert)   { described_class.parse_openssh(fixture("ecdsa_leaf_for_rsa_ca-cert.pub")) }
+  let(:ed25519_cert) { described_class.parse_openssh(fixture("ed25519_leaf_for_rsa_ca-cert.pub")) }
 
-  let(:rsa_ca_cert)     { described_class.parse(fixture("rsa_leaf_for_rsa_ca-cert.pub")) }
-  let(:dsa_ca_cert)     { described_class.parse(fixture("rsa_leaf_for_dsa_ca-cert.pub")) }
-  let(:ecdsa_ca_cert)   { described_class.parse(fixture("rsa_leaf_for_ecdsa_ca-cert.pub")) }
-  let(:ed25519_ca_cert) { described_class.parse(fixture("rsa_leaf_for_ed25519_ca-cert.pub")) }
+  let(:rsa_ca_cert)     { described_class.parse_openssh(fixture("rsa_leaf_for_rsa_ca-cert.pub")) }
+  let(:dsa_ca_cert)     { described_class.parse_openssh(fixture("rsa_leaf_for_dsa_ca-cert.pub")) }
+  let(:ecdsa_ca_cert)   { described_class.parse_openssh(fixture("rsa_leaf_for_ecdsa_ca-cert.pub")) }
+  let(:ed25519_ca_cert) { described_class.parse_openssh(fixture("rsa_leaf_for_ed25519_ca-cert.pub")) }
 
   let(:min_time) { Time.at(0) }
   let(:max_time) { Time.at((2**64)-1) }
 
+  it "supports the deprecated Certificate.parse method" do
+    expect {
+      described_class.parse(fixture("rsa_leaf_for_rsa_ca-cert.pub"))
+    }.not_to raise_error
+  end
+
   it "raises on invalid signatures" do
     expect {
-      described_class.parse(fixture("bad_signature-cert.pub"))
+      described_class.parse_openssh(fixture("bad_signature-cert.pub"))
     }.to raise_error(SSHData::VerifyError)
   end
 
   it "doesn't validate signatures if provided unsafe_no_verify flag" do
     expect {
-      described_class.parse(fixture("bad_signature-cert.pub"),
+      described_class.parse_openssh(fixture("bad_signature-cert.pub"),
         unsafe_no_verify: true
       )
     }.not_to raise_error
   end
 
   it "raises on trailing data" do
-    algo, b64, host = fixture("rsa_leaf_for_rsa_ca-cert.pub").split(" ", 3)
+    algo, b64, comment = fixture("rsa_leaf_for_rsa_ca-cert.pub").split(" ", 3)
     raw = Base64.decode64(b64)
     raw += "foobar"
     b64 = Base64.strict_encode64(raw)
-    cert = [algo, b64, host].join(" ")
+    cert = [algo, b64, comment].join(" ")
 
     expect {
-      described_class.parse(cert, unsafe_no_verify: true)
+      described_class.parse_openssh(cert, unsafe_no_verify: true)
     }.to raise_error(SSHData::DecodeError)
   end
 
   it "raises on type mismatch" do
-    _, b64, host = fixture("rsa_leaf_for_rsa_ca-cert.pub").split(" ", 3)
-    cert = [SSHData::Certificate::ALGO_ED25519, b64, host].join(" ")
+    _, b64, comment = fixture("rsa_leaf_for_rsa_ca-cert.pub").split(" ", 3)
+    cert = [SSHData::Certificate::ALGO_ED25519, b64, comment].join(" ")
 
     expect {
-      described_class.parse(cert, unsafe_no_verify: true)
+      described_class.parse_openssh(cert, unsafe_no_verify: true)
     }.to raise_error(SSHData::DecodeError)
   end
 
-  it "doesn't require the user/host names" do
+  it "doesn't require the comment" do
     type, b64, _ = fixture("rsa_leaf_for_rsa_ca-cert.pub").split(" ", 3)
     cert = [type, b64].join(" ")
 
     expect {
-      described_class.parse(cert, unsafe_no_verify: true)
+      described_class.parse_openssh(cert, unsafe_no_verify: true)
     }.not_to raise_error
   end
 
diff --git a/spec/encoding_spec.rb b/spec/encoding_spec.rb
index 2933a9b..d24cbf4 100644
--- a/spec/encoding_spec.rb
+++ b/spec/encoding_spec.rb
@@ -110,7 +110,7 @@
       expect(rsa_data[:public_keys]).to be_a(Array)
       expect(rsa_data[:public_keys].length).to eq(1)
       expect {
-        SSHData::PublicKey.parse_raw(rsa_data[:public_keys].first)
+        SSHData::PublicKey.parse_rfc4253(rsa_data[:public_keys].first)
       }.not_to raise_error
 
       expect(rsa_data[:checkint1]).to be_a(Integer)
@@ -133,7 +133,7 @@
       expect(dsa_data[:public_keys]).to be_a(Array)
       expect(dsa_data[:public_keys].length).to eq(1)
       expect {
-        SSHData::PublicKey.parse_raw(dsa_data[:public_keys].first)
+        SSHData::PublicKey.parse_rfc4253(dsa_data[:public_keys].first)
       }.not_to raise_error
 
       expect(dsa_data[:checkint1]).to be_a(Integer)
@@ -156,7 +156,7 @@
       expect(ecdsa_data[:public_keys]).to be_a(Array)
       expect(ecdsa_data[:public_keys].length).to eq(1)
       expect {
-        SSHData::PublicKey.parse_raw(ecdsa_data[:public_keys].first)
+        SSHData::PublicKey.parse_rfc4253(ecdsa_data[:public_keys].first)
       }.not_to raise_error
 
       expect(ecdsa_data[:checkint1]).to be_a(Integer)
@@ -179,7 +179,7 @@
       expect(ed25519_data[:public_keys]).to be_a(Array)
       expect(ed25519_data[:public_keys].length).to eq(1)
       expect {
-        SSHData::PublicKey.parse_raw(ed25519_data[:public_keys].first)
+        SSHData::PublicKey.parse_rfc4253(ed25519_data[:public_keys].first)
       }.not_to raise_error
 
       expect(ed25519_data[:checkint1]).to be_a(Integer)
diff --git a/spec/fixtures/gen.sh b/spec/fixtures/gen.sh
index 888503f..a2b4d20 100755
--- a/spec/fixtures/gen.sh
+++ b/spec/fixtures/gen.sh
@@ -41,14 +41,14 @@ ruby <<RUBY
 require "base64"
 
 encoded = File.read("rsa_leaf_for_ed25519_ca-cert.pub")
-algo, b64, host = encoded.split(" ", 3)
+algo, b64, comment = encoded.split(" ", 3)
 raw = Base64.decode64(b64)
 
 # we flip bits in the last byte, since that's where the signature is.
 raw[-1] = (raw[-1].ord ^ 0xff).chr
 
 b64 = Base64.strict_encode64(raw)
-encoded = [algo, b64, host].join(" ")
+encoded = [algo, b64, comment].join(" ")
 
 File.open("bad_signature-cert.pub", "w") { |f| f.write(encoded) }
 RUBY
diff --git a/spec/public_key/dsa_spec.rb b/spec/public_key/dsa_spec.rb
index 5d2f57c..4d12373 100644
--- a/spec/public_key/dsa_spec.rb
+++ b/spec/public_key/dsa_spec.rb
@@ -11,7 +11,7 @@
   let(:ssh_sig)     { described_class.ssh_signature(openssl_sig) }
   let(:sig)         { SSHData::Encoding.encode_signature(SSHData::PublicKey::ALGO_DSA, ssh_sig) }
 
-  let(:openssh_key) { SSHData::PublicKey.parse(fixture("dsa_leaf_for_rsa_ca.pub")) }
+  let(:openssh_key) { SSHData::PublicKey.parse_openssh(fixture("dsa_leaf_for_rsa_ca.pub")) }
 
   subject do
     described_class.new(
@@ -92,7 +92,7 @@
 
   it "can verify certificate signatures" do
     expect {
-      SSHData::Certificate.parse(fixture("rsa_leaf_for_dsa_ca-cert.pub"),
+      SSHData::Certificate.parse_openssh(fixture("rsa_leaf_for_dsa_ca-cert.pub"),
         unsafe_no_verify: false
       )
     }.not_to raise_error
diff --git a/spec/public_key/ecdsa_spec.rb b/spec/public_key/ecdsa_spec.rb
index 78d4d63..fc0176b 100644
--- a/spec/public_key/ecdsa_spec.rb
+++ b/spec/public_key/ecdsa_spec.rb
@@ -1,7 +1,7 @@
 require_relative "../spec_helper"
 
 describe SSHData::PublicKey::ECDSA do
-  let(:openssh_key) { SSHData::PublicKey.parse(fixture("ecdsa_leaf_for_rsa_ca.pub")) }
+  let(:openssh_key) { SSHData::PublicKey.parse_openssh(fixture("ecdsa_leaf_for_rsa_ca.pub")) }
 
   it "can parse openssh-generate keys" do
     expect { openssh_key }.not_to raise_error
@@ -13,7 +13,7 @@
 
   it "can verify certificate signatures" do
     expect {
-      SSHData::Certificate.parse(fixture("rsa_leaf_for_ecdsa_ca-cert.pub"),
+      SSHData::Certificate.parse_openssh(fixture("rsa_leaf_for_ecdsa_ca-cert.pub"),
         unsafe_no_verify: false
       )
     }.not_to raise_error
@@ -29,7 +29,7 @@
     ].join)].join(" ")
 
     expect {
-      SSHData::PublicKey.parse(malformed)
+      SSHData::PublicKey.parse_openssh(malformed)
     }.to raise_error(SSHData::DecodeError)
   end
 
@@ -107,7 +107,7 @@
         ].join)].join(" ")
 
         expect {
-          SSHData::PublicKey.parse(malformed)
+          SSHData::PublicKey.parse_openssh(malformed)
         }.to raise_error(SSHData::DecodeError)
       end
     end
diff --git a/spec/public_key/ed25519_spec.rb b/spec/public_key/ed25519_spec.rb
index f426059..0ada4e8 100644
--- a/spec/public_key/ed25519_spec.rb
+++ b/spec/public_key/ed25519_spec.rb
@@ -8,7 +8,7 @@
   let(:raw_sig) { signing_key.sign(msg) }
   let(:sig)     { SSHData::Encoding.encode_signature(SSHData::PublicKey::ALGO_ED25519, raw_sig) }
 
-  let(:openssh_key) { SSHData::PublicKey.parse(fixture("ed25519_leaf_for_rsa_ca.pub")) }
+  let(:openssh_key) { SSHData::PublicKey.parse_openssh(fixture("ed25519_leaf_for_rsa_ca.pub")) }
 
   subject do
     described_class.new(
@@ -59,7 +59,7 @@
 
   it "can verify certificate signatures" do
     expect {
-      SSHData::Certificate.parse(fixture("rsa_leaf_for_ed25519_ca-cert.pub"),
+      SSHData::Certificate.parse_openssh(fixture("rsa_leaf_for_ed25519_ca-cert.pub"),
         unsafe_no_verify: false
       )
     }.not_to raise_error
@@ -72,7 +72,7 @@
 
     begin
       expect {
-        SSHData::Certificate.parse(fixture("rsa_leaf_for_ed25519_ca-cert.pub"),
+        SSHData::Certificate.parse_openssh(fixture("rsa_leaf_for_ed25519_ca-cert.pub"),
           unsafe_no_verify: false
         )
       }.to raise_error(SSHData::VerifyError)
diff --git a/spec/public_key/rsa_spec.rb b/spec/public_key/rsa_spec.rb
index 379051d..5b4f930 100644
--- a/spec/public_key/rsa_spec.rb
+++ b/spec/public_key/rsa_spec.rb
@@ -10,7 +10,7 @@
   let(:raw_sig) { private_key.sign(digest, msg) }
   let(:sig)     { SSHData::Encoding.encode_signature(SSHData::PublicKey::ALGO_RSA, raw_sig) }
 
-  let(:openssh_key) { SSHData::PublicKey.parse(fixture("rsa_leaf_for_rsa_ca.pub")) }
+  let(:openssh_key) { SSHData::PublicKey.parse_openssh(fixture("rsa_leaf_for_rsa_ca.pub")) }
 
   subject do
     described_class.new(
@@ -65,7 +65,7 @@
 
   it "can verify certificate signatures" do
     expect {
-      SSHData::Certificate.parse(fixture("rsa_leaf_for_rsa_ca-cert.pub"),
+      SSHData::Certificate.parse_openssh(fixture("rsa_leaf_for_rsa_ca-cert.pub"),
         unsafe_no_verify: false
       )
     }.not_to raise_error
diff --git a/spec/public_key_spec.rb b/spec/public_key_spec.rb
index 9f0521f..7671572 100644
--- a/spec/public_key_spec.rb
+++ b/spec/public_key_spec.rb
@@ -1,15 +1,32 @@
 require_relative "./spec_helper"
 
 describe SSHData::PublicKey do
+  it "supports the deprecated PublicKey.parse method" do
+    expect {
+      described_class.parse(fixture("rsa_leaf_for_rsa_ca.pub"))
+    }.not_to raise_error
+  end
+
   Dir["spec/fixtures/*ca.pub"].each do |path|
     name = File.basename(path)
 
-    it "generates a MD5 fingerprint matching ssh-keygen for #{name}" do
-      expect(described_class.parse(fixture(name)).fingerprint(md5: true)).to eq(ssh_keygen_fingerprint(name, :md5))
-    end
+    describe name do
+      let(:openssh) { fixture(name).strip }
+      let(:comment) { SSHData.key_parts(openssh).last }
+
+      subject { described_class.parse_openssh(openssh) }
+
+      it "generates a MD5 fingerprint matching ssh-keygen" do
+        expect(subject.fingerprint(md5: true)).to eq(ssh_keygen_fingerprint(name, :md5))
+      end
+
+      it "generates a SHA256 fingerprint matching ssh-keygen" do
+        expect(subject.fingerprint).to eq(ssh_keygen_fingerprint(name, :sha256))
+      end
 
-    it "generates a SHA256 fingerprint matching ssh-keygen for #{name}" do
-      expect(described_class.parse(fixture(name)).fingerprint).to eq(ssh_keygen_fingerprint(name, :sha256))
+      it "can re-encode back into authorized_keys format" do
+        expect(subject.openssh(comment: comment)).to eq(openssh)
+      end
     end
   end
 end