| :mod:`ssl` --- TLS/SSL wrapper for socket objects |
| ================================================= |
| |
| .. module:: ssl |
| :synopsis: TLS/SSL wrapper for socket objects |
| |
| .. moduleauthor:: Bill Janssen <bill.janssen@gmail.com> |
| .. sectionauthor:: Bill Janssen <bill.janssen@gmail.com> |
| |
| |
| .. index:: single: OpenSSL; (use in module ssl) |
| |
| .. index:: TLS, SSL, Transport Layer Security, Secure Sockets Layer |
| |
| This module provides access to Transport Layer Security (often known as "Secure |
| Sockets Layer") encryption and peer authentication facilities for network |
| sockets, both client-side and server-side. This module uses the OpenSSL |
| library. It is available on all modern Unix systems, Windows, Mac OS X, and |
| probably additional platforms, as long as OpenSSL is installed on that platform. |
| |
| .. note:: |
| |
| Some behavior may be platform dependent, since calls are made to the |
| operating system socket APIs. The installed version of OpenSSL may also |
| cause variations in behavior. |
| |
| This section documents the objects and functions in the ``ssl`` module; for more |
| general information about TLS, SSL, and certificates, the reader is referred to |
| the documents in the "See Also" section at the bottom. |
| |
| This module provides a class, :class:`ssl.SSLSocket`, which is derived from the |
| :class:`socket.socket` type, and provides a socket-like wrapper that also |
| encrypts and decrypts the data going over the socket with SSL. It supports |
| additional :meth:`read` and :meth:`write` methods, along with a method, |
| :meth:`getpeercert`, to retrieve the certificate of the other side of the |
| connection, and a method, :meth:`cipher`, to retrieve the cipher being used for |
| the secure connection. |
| |
| Functions, Constants, and Exceptions |
| ------------------------------------ |
| |
| .. exception:: SSLError |
| |
| Raised to signal an error from the underlying SSL implementation. This |
| signifies some problem in the higher-level encryption and authentication |
| layer that's superimposed on the underlying network connection. This error |
| is a subtype of :exc:`socket.error`, which in turn is a subtype of |
| :exc:`IOError`. |
| |
| .. function:: wrap_socket(sock, keyfile=None, certfile=None, server_side=False, cert_reqs=CERT_NONE, ssl_version={see docs}, ca_certs=None, do_handshake_on_connect=True, suppress_ragged_eofs=True) |
| |
| Takes an instance ``sock`` of :class:`socket.socket`, and returns an instance |
| of :class:`ssl.SSLSocket`, a subtype of :class:`socket.socket`, which wraps |
| the underlying socket in an SSL context. For client-side sockets, the |
| context construction is lazy; if the underlying socket isn't connected yet, |
| the context construction will be performed after :meth:`connect` is called on |
| the socket. For server-side sockets, if the socket has no remote peer, it is |
| assumed to be a listening socket, and the server-side SSL wrapping is |
| automatically performed on client connections accepted via the :meth:`accept` |
| method. :func:`wrap_socket` may raise :exc:`SSLError`. |
| |
| The ``keyfile`` and ``certfile`` parameters specify optional files which |
| contain a certificate to be used to identify the local side of the |
| connection. See the discussion of :ref:`ssl-certificates` for more |
| information on how the certificate is stored in the ``certfile``. |
| |
| Often the private key is stored in the same file as the certificate; in this |
| case, only the ``certfile`` parameter need be passed. If the private key is |
| stored in a separate file, both parameters must be used. If the private key |
| is stored in the ``certfile``, it should come before the first certificate in |
| the certificate chain:: |
| |
| -----BEGIN RSA PRIVATE KEY----- |
| ... (private key in base64 encoding) ... |
| -----END RSA PRIVATE KEY----- |
| -----BEGIN CERTIFICATE----- |
| ... (certificate in base64 PEM encoding) ... |
| -----END CERTIFICATE----- |
| |
| The parameter ``server_side`` is a boolean which identifies whether |
| server-side or client-side behavior is desired from this socket. |
| |
| The parameter ``cert_reqs`` specifies whether a certificate is required from |
| the other side of the connection, and whether it will be validated if |
| provided. It must be one of the three values :const:`CERT_NONE` |
| (certificates ignored), :const:`CERT_OPTIONAL` (not required, but validated |
| if provided), or :const:`CERT_REQUIRED` (required and validated). If the |
| value of this parameter is not :const:`CERT_NONE`, then the ``ca_certs`` |
| parameter must point to a file of CA certificates. |
| |
| The ``ca_certs`` file contains a set of concatenated "certification |
| authority" certificates, which are used to validate certificates passed from |
| the other end of the connection. See the discussion of |
| :ref:`ssl-certificates` for more information about how to arrange the |
| certificates in this file. |
| |
| The parameter ``ssl_version`` specifies which version of the SSL protocol to |
| use. Typically, the server chooses a particular protocol version, and the |
| client must adapt to the server's choice. Most of the versions are not |
| interoperable with the other versions. If not specified, for client-side |
| operation, the default SSL version is SSLv3; for server-side operation, |
| SSLv23. These version selections provide the most compatibility with other |
| versions. |
| |
| Here's a table showing which versions in a client (down the side) can connect |
| to which versions in a server (along the top): |
| |
| .. table:: |
| |
| ======================== ========= ========= ========== ========= |
| *client* / **server** **SSLv2** **SSLv3** **SSLv23** **TLSv1** |
| ------------------------ --------- --------- ---------- --------- |
| *SSLv2* yes no yes* no |
| *SSLv3* yes yes yes no |
| *SSLv23* yes no yes no |
| *TLSv1* no no yes yes |
| ======================== ========= ========= ========== ========= |
| |
| In some older versions of OpenSSL (for instance, 0.9.7l on OS X 10.4), an |
| SSLv2 client could not connect to an SSLv23 server. |
| |
| The parameter ``do_handshake_on_connect`` specifies whether to do the SSL |
| handshake automatically after doing a :meth:`socket.connect`, or whether the |
| application program will call it explicitly, by invoking the |
| :meth:`SSLSocket.do_handshake` method. Calling |
| :meth:`SSLSocket.do_handshake` explicitly gives the program control over the |
| blocking behavior of the socket I/O involved in the handshake. |
| |
| The parameter ``suppress_ragged_eofs`` specifies how the |
| :meth:`SSLSocket.read` method should signal unexpected EOF from the other end |
| of the connection. If specified as :const:`True` (the default), it returns a |
| normal EOF in response to unexpected EOF errors raised from the underlying |
| socket; if :const:`False`, it will raise the exceptions back to the caller. |
| |
| .. function:: RAND_status() |
| |
| Returns True if the SSL pseudo-random number generator has been seeded with |
| 'enough' randomness, and False otherwise. You can use :func:`ssl.RAND_egd` |
| and :func:`ssl.RAND_add` to increase the randomness of the pseudo-random |
| number generator. |
| |
| .. function:: RAND_egd(path) |
| |
| If you are running an entropy-gathering daemon (EGD) somewhere, and ``path`` |
| is the pathname of a socket connection open to it, this will read 256 bytes |
| of randomness from the socket, and add it to the SSL pseudo-random number |
| generator to increase the security of generated secret keys. This is |
| typically only necessary on systems without better sources of randomness. |
| |
| See http://egd.sourceforge.net/ or http://prngd.sourceforge.net/ for sources |
| of entropy-gathering daemons. |
| |
| .. function:: RAND_add(bytes, entropy) |
| |
| Mixes the given ``bytes`` into the SSL pseudo-random number generator. The |
| parameter ``entropy`` (a float) is a lower bound on the entropy contained in |
| string (so you can always use :const:`0.0`). See :rfc:`1750` for more |
| information on sources of entropy. |
| |
| .. function:: cert_time_to_seconds(timestring) |
| |
| Returns a floating-point value containing a normal seconds-after-the-epoch |
| time value, given the time-string representing the "notBefore" or "notAfter" |
| date from a certificate. |
| |
| Here's an example:: |
| |
| >>> import ssl |
| >>> ssl.cert_time_to_seconds("May 9 00:00:00 2007 GMT") |
| 1178694000.0 |
| >>> import time |
| >>> time.ctime(ssl.cert_time_to_seconds("May 9 00:00:00 2007 GMT")) |
| 'Wed May 9 00:00:00 2007' |
| >>> |
| |
| .. function:: get_server_certificate(addr, ssl_version=PROTOCOL_SSLv3, ca_certs=None) |
| |
| Given the address ``addr`` of an SSL-protected server, as a (*hostname*, |
| *port-number*) pair, fetches the server's certificate, and returns it as a |
| PEM-encoded string. If ``ssl_version`` is specified, uses that version of |
| the SSL protocol to attempt to connect to the server. If ``ca_certs`` is |
| specified, it should be a file containing a list of root certificates, the |
| same format as used for the same parameter in :func:`wrap_socket`. The call |
| will attempt to validate the server certificate against that set of root |
| certificates, and will fail if the validation attempt fails. |
| |
| .. function:: DER_cert_to_PEM_cert(DER_cert_bytes) |
| |
| Given a certificate as a DER-encoded blob of bytes, returns a PEM-encoded |
| string version of the same certificate. |
| |
| .. function:: PEM_cert_to_DER_cert(PEM_cert_string) |
| |
| Given a certificate as an ASCII PEM string, returns a DER-encoded sequence of |
| bytes for that same certificate. |
| |
| .. data:: CERT_NONE |
| |
| Value to pass to the ``cert_reqs`` parameter to :func:`sslobject` when no |
| certificates will be required or validated from the other side of the socket |
| connection. |
| |
| .. data:: CERT_OPTIONAL |
| |
| Value to pass to the ``cert_reqs`` parameter to :func:`sslobject` when no |
| certificates will be required from the other side of the socket connection, |
| but if they are provided, will be validated. Note that use of this setting |
| requires a valid certificate validation file also be passed as a value of the |
| ``ca_certs`` parameter. |
| |
| .. data:: CERT_REQUIRED |
| |
| Value to pass to the ``cert_reqs`` parameter to :func:`sslobject` when |
| certificates will be required from the other side of the socket connection. |
| Note that use of this setting requires a valid certificate validation file |
| also be passed as a value of the ``ca_certs`` parameter. |
| |
| .. data:: PROTOCOL_SSLv2 |
| |
| Selects SSL version 2 as the channel encryption protocol. |
| |
| .. warning:: |
| |
| SSL version 2 is insecure. Its use is highly discouraged. |
| |
| .. data:: PROTOCOL_SSLv23 |
| |
| Selects SSL version 2 or 3 as the channel encryption protocol. This is a |
| setting to use with servers for maximum compatibility with the other end of |
| an SSL connection, but it may cause the specific ciphers chosen for the |
| encryption to be of fairly low quality. |
| |
| .. data:: PROTOCOL_SSLv3 |
| |
| Selects SSL version 3 as the channel encryption protocol. For clients, this |
| is the maximally compatible SSL variant. |
| |
| .. data:: PROTOCOL_TLSv1 |
| |
| Selects TLS version 1 as the channel encryption protocol. This is the most |
| modern version, and probably the best choice for maximum protection, if both |
| sides can speak it. |
| |
| |
| SSLSocket Objects |
| ----------------- |
| |
| .. method:: SSLSocket.read(nbytes=1024, buffer=None) |
| |
| Reads up to ``nbytes`` bytes from the SSL-encrypted channel and returns them. |
| If the ``buffer`` is specified, it will attempt to read into the buffer the |
| minimum of the size of the buffer and ``nbytes``, if that is specified. If |
| no buffer is specified, an immutable buffer is allocated and returned with |
| the data read from the socket. |
| |
| .. method:: SSLSocket.write(data) |
| |
| Writes the ``data`` to the other side of the connection, using the SSL |
| channel to encrypt. Returns the number of bytes written. |
| |
| .. method:: SSLSocket.do_handshake() |
| |
| Performs the SSL setup handshake. If the socket is non-blocking, this method |
| may raise :exc:`SSLError` with the value of the exception instance's |
| ``args[0]`` being either :const:`SSL_ERROR_WANT_READ` or |
| :const:`SSL_ERROR_WANT_WRITE`, and should be called again until it stops |
| raising those exceptions. Here's an example of how to do that:: |
| |
| while True: |
| try: |
| sock.do_handshake() |
| break |
| except ssl.SSLError as err: |
| if err.args[0] == ssl.SSL_ERROR_WANT_READ: |
| select.select([sock], [], []) |
| elif err.args[0] == ssl.SSL_ERROR_WANT_WRITE: |
| select.select([], [sock], []) |
| else: |
| raise |
| |
| .. method:: SSLSocket.getpeercert(binary_form=False) |
| |
| If there is no certificate for the peer on the other end of the connection, |
| returns ``None``. |
| |
| If the parameter ``binary_form`` is :const:`False`, and a certificate was |
| received from the peer, this method returns a :class:`dict` instance. If the |
| certificate was not validated, the dict is empty. If the certificate was |
| validated, it returns a dict with the keys ``subject`` (the principal for |
| which the certificate was issued), and ``notAfter`` (the time after which the |
| certificate should not be trusted). The certificate was already validated, |
| so the ``notBefore`` and ``issuer`` fields are not returned. If a |
| certificate contains an instance of the *Subject Alternative Name* extension |
| (see :rfc:`3280`), there will also be a ``subjectAltName`` key in the |
| dictionary. |
| |
| The "subject" field is a tuple containing the sequence of relative |
| distinguished names (RDNs) given in the certificate's data structure for the |
| principal, and each RDN is a sequence of name-value pairs:: |
| |
| {'notAfter': 'Feb 16 16:54:50 2013 GMT', |
| 'subject': ((('countryName', 'US'),), |
| (('stateOrProvinceName', 'Delaware'),), |
| (('localityName', 'Wilmington'),), |
| (('organizationName', 'Python Software Foundation'),), |
| (('organizationalUnitName', 'SSL'),), |
| (('commonName', 'somemachine.python.org'),))} |
| |
| If the ``binary_form`` parameter is :const:`True`, and a certificate was |
| provided, this method returns the DER-encoded form of the entire certificate |
| as a sequence of bytes, or :const:`None` if the peer did not provide a |
| certificate. This return value is independent of validation; if validation |
| was required (:const:`CERT_OPTIONAL` or :const:`CERT_REQUIRED`), it will have |
| been validated, but if :const:`CERT_NONE` was used to establish the |
| connection, the certificate, if present, will not have been validated. |
| |
| .. method:: SSLSocket.cipher() |
| |
| Returns a three-value tuple containing the name of the cipher being used, the |
| version of the SSL protocol that defines its use, and the number of secret |
| bits being used. If no connection has been established, returns ``None``. |
| |
| |
| .. method:: SSLSocket.unwrap() |
| |
| Performs the SSL shutdown handshake, which removes the TLS layer from the |
| underlying socket, and returns the underlying socket object. This can be |
| used to go from encrypted operation over a connection to unencrypted. The |
| returned socket should always be used for further communication with the |
| other side of the connection, rather than the original socket. |
| |
| .. index:: single: certificates |
| |
| .. index:: single: X509 certificate |
| |
| .. _ssl-certificates: |
| |
| Certificates |
| ------------ |
| |
| Certificates in general are part of a public-key / private-key system. In this |
| system, each *principal*, (which may be a machine, or a person, or an |
| organization) is assigned a unique two-part encryption key. One part of the key |
| is public, and is called the *public key*; the other part is kept secret, and is |
| called the *private key*. The two parts are related, in that if you encrypt a |
| message with one of the parts, you can decrypt it with the other part, and |
| **only** with the other part. |
| |
| A certificate contains information about two principals. It contains the name |
| of a *subject*, and the subject's public key. It also contains a statement by a |
| second principal, the *issuer*, that the subject is who he claims to be, and |
| that this is indeed the subject's public key. The issuer's statement is signed |
| with the issuer's private key, which only the issuer knows. However, anyone can |
| verify the issuer's statement by finding the issuer's public key, decrypting the |
| statement with it, and comparing it to the other information in the certificate. |
| The certificate also contains information about the time period over which it is |
| valid. This is expressed as two fields, called "notBefore" and "notAfter". |
| |
| In the Python use of certificates, a client or server can use a certificate to |
| prove who they are. The other side of a network connection can also be required |
| to produce a certificate, and that certificate can be validated to the |
| satisfaction of the client or server that requires such validation. The |
| connection attempt can be set to raise an exception if the validation fails. |
| Validation is done automatically, by the underlying OpenSSL framework; the |
| application need not concern itself with its mechanics. But the application |
| does usually need to provide sets of certificates to allow this process to take |
| place. |
| |
| Python uses files to contain certificates. They should be formatted as "PEM" |
| (see :rfc:`1422`), which is a base-64 encoded form wrapped with a header line |
| and a footer line:: |
| |
| -----BEGIN CERTIFICATE----- |
| ... (certificate in base64 PEM encoding) ... |
| -----END CERTIFICATE----- |
| |
| The Python files which contain certificates can contain a sequence of |
| certificates, sometimes called a *certificate chain*. This chain should start |
| with the specific certificate for the principal who "is" the client or server, |
| and then the certificate for the issuer of that certificate, and then the |
| certificate for the issuer of *that* certificate, and so on up the chain till |
| you get to a certificate which is *self-signed*, that is, a certificate which |
| has the same subject and issuer, sometimes called a *root certificate*. The |
| certificates should just be concatenated together in the certificate file. For |
| example, suppose we had a three certificate chain, from our server certificate |
| to the certificate of the certification authority that signed our server |
| certificate, to the root certificate of the agency which issued the |
| certification authority's certificate:: |
| |
| -----BEGIN CERTIFICATE----- |
| ... (certificate for your server)... |
| -----END CERTIFICATE----- |
| -----BEGIN CERTIFICATE----- |
| ... (the certificate for the CA)... |
| -----END CERTIFICATE----- |
| -----BEGIN CERTIFICATE----- |
| ... (the root certificate for the CA's issuer)... |
| -----END CERTIFICATE----- |
| |
| If you are going to require validation of the other side of the connection's |
| certificate, you need to provide a "CA certs" file, filled with the certificate |
| chains for each issuer you are willing to trust. Again, this file just contains |
| these chains concatenated together. For validation, Python will use the first |
| chain it finds in the file which matches. Some "standard" root certificates are |
| available from various certification authorities: `CACert.org |
| <http://www.cacert.org/index.php?id=3>`_, `Thawte |
| <http://www.thawte.com/roots/>`_, `Verisign |
| <http://www.verisign.com/support/roots.html>`_, `Positive SSL |
| <http://www.PositiveSSL.com/ssl-certificate-support/cert_installation/UTN-USERFirst-Hardware.crt>`_ |
| (used by python.org), `Equifax and GeoTrust |
| <http://www.geotrust.com/resources/root_certificates/index.asp>`_. |
| |
| In general, if you are using SSL3 or TLS1, you don't need to put the full chain |
| in your "CA certs" file; you only need the root certificates, and the remote |
| peer is supposed to furnish the other certificates necessary to chain from its |
| certificate to a root certificate. See :rfc:`4158` for more discussion of the |
| way in which certification chains can be built. |
| |
| If you are going to create a server that provides SSL-encrypted connection |
| services, you will need to acquire a certificate for that service. There are |
| many ways of acquiring appropriate certificates, such as buying one from a |
| certification authority. Another common practice is to generate a self-signed |
| certificate. The simplest way to do this is with the OpenSSL package, using |
| something like the following:: |
| |
| % openssl req -new -x509 -days 365 -nodes -out cert.pem -keyout cert.pem |
| Generating a 1024 bit RSA private key |
| .......++++++ |
| .............................++++++ |
| writing new private key to 'cert.pem' |
| ----- |
| You are about to be asked to enter information that will be incorporated |
| into your certificate request. |
| What you are about to enter is what is called a Distinguished Name or a DN. |
| There are quite a few fields but you can leave some blank |
| For some fields there will be a default value, |
| If you enter '.', the field will be left blank. |
| ----- |
| Country Name (2 letter code) [AU]:US |
| State or Province Name (full name) [Some-State]:MyState |
| Locality Name (eg, city) []:Some City |
| Organization Name (eg, company) [Internet Widgits Pty Ltd]:My Organization, Inc. |
| Organizational Unit Name (eg, section) []:My Group |
| Common Name (eg, YOUR name) []:myserver.mygroup.myorganization.com |
| Email Address []:ops@myserver.mygroup.myorganization.com |
| % |
| |
| The disadvantage of a self-signed certificate is that it is its own root |
| certificate, and no one else will have it in their cache of known (and trusted) |
| root certificates. |
| |
| |
| Examples |
| -------- |
| |
| Testing for SSL support |
| ^^^^^^^^^^^^^^^^^^^^^^^ |
| |
| To test for the presence of SSL support in a Python installation, user code |
| should use the following idiom:: |
| |
| try: |
| import ssl |
| except ImportError: |
| pass |
| else: |
| ... # do something that requires SSL support |
| |
| Client-side operation |
| ^^^^^^^^^^^^^^^^^^^^^ |
| |
| This example connects to an SSL server, prints the server's address and |
| certificate, sends some bytes, and reads part of the response:: |
| |
| import socket, ssl, pprint |
| |
| s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) |
| |
| # require a certificate from the server |
| ssl_sock = ssl.wrap_socket(s, |
| ca_certs="/etc/ca_certs_file", |
| cert_reqs=ssl.CERT_REQUIRED) |
| |
| ssl_sock.connect(('www.verisign.com', 443)) |
| |
| print(repr(ssl_sock.getpeername())) |
| pprint.pprint(ssl_sock.getpeercert()) |
| print(pprint.pformat(ssl_sock.getpeercert())) |
| |
| # Set a simple HTTP request -- use http.client in actual code. |
| ssl_sock.write("""GET / HTTP/1.0\r |
| Host: www.verisign.com\r\n\r\n""") |
| |
| # Read a chunk of data. Will not necessarily |
| # read all the data returned by the server. |
| data = ssl_sock.read() |
| |
| # note that closing the SSLSocket will also close the underlying socket |
| ssl_sock.close() |
| |
| As of September 6, 2007, the certificate printed by this program looked like |
| this:: |
| |
| {'notAfter': 'May 8 23:59:59 2009 GMT', |
| 'subject': ((('serialNumber', '2497886'),), |
| (('1.3.6.1.4.1.311.60.2.1.3', 'US'),), |
| (('1.3.6.1.4.1.311.60.2.1.2', 'Delaware'),), |
| (('countryName', 'US'),), |
| (('postalCode', '94043'),), |
| (('stateOrProvinceName', 'California'),), |
| (('localityName', 'Mountain View'),), |
| (('streetAddress', '487 East Middlefield Road'),), |
| (('organizationName', 'VeriSign, Inc.'),), |
| (('organizationalUnitName', |
| 'Production Security Services'),), |
| (('organizationalUnitName', |
| 'Terms of use at www.verisign.com/rpa (c)06'),), |
| (('commonName', 'www.verisign.com'),))} |
| |
| which is a fairly poorly-formed ``subject`` field. |
| |
| Server-side operation |
| ^^^^^^^^^^^^^^^^^^^^^ |
| |
| For server operation, typically you'd need to have a server certificate, and |
| private key, each in a file. You'd open a socket, bind it to a port, call |
| :meth:`listen` on it, then start waiting for clients to connect:: |
| |
| import socket, ssl |
| |
| bindsocket = socket.socket() |
| bindsocket.bind(('myaddr.mydomain.com', 10023)) |
| bindsocket.listen(5) |
| |
| When one did, you'd call :meth:`accept` on the socket to get the new socket from |
| the other end, and use :func:`wrap_socket` to create a server-side SSL context |
| for it:: |
| |
| while True: |
| newsocket, fromaddr = bindsocket.accept() |
| connstream = ssl.wrap_socket(newsocket, |
| server_side=True, |
| certfile="mycertfile", |
| keyfile="mykeyfile", |
| ssl_version=ssl.PROTOCOL_TLSv1) |
| try: |
| deal_with_client(connstream) |
| finally: |
| connstream.shutdown(socket.SHUT_RDWR) |
| connstream.close() |
| |
| Then you'd read data from the ``connstream`` and do something with it till you |
| are finished with the client (or the client is finished with you):: |
| |
| def deal_with_client(connstream): |
| data = connstream.read() |
| # null data means the client is finished with us |
| while data: |
| if not do_something(connstream, data): |
| # we'll assume do_something returns False |
| # when we're finished with client |
| break |
| data = connstream.read() |
| # finished with client |
| |
| And go back to listening for new client connections. |
| |
| |
| .. seealso:: |
| |
| Class :class:`socket.socket` |
| Documentation of underlying :mod:`socket` class |
| |
| `Introducing SSL and Certificates using OpenSSL <http://old.pseudonym.org/ssl/wwwj-index.html>`_ |
| Frederick J. Hirsch |
| |
| `RFC 1422: Privacy Enhancement for Internet Electronic Mail: Part II: Certificate-Based Key Management <http://www.ietf.org/rfc/rfc1422>`_ |
| Steve Kent |
| |
| `RFC 1750: Randomness Recommendations for Security <http://www.ietf.org/rfc/rfc1750>`_ |
| D. Eastlake et. al. |
| |
| `RFC 3280: Internet X.509 Public Key Infrastructure Certificate and CRL Profile <http://www.ietf.org/rfc/rfc3280>`_ |
| Housley et. al. |