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Secure Sockets Layer Discussion List FAQ



Frequently Asked Questions about technical implementation issues of the Secure Sockets Layer protocol.

This FAQ about technical implementation issues of the Secure Sockets Layer protocol was compiled and written by Shannon Appel SAppel@consensus.com with numerous contributions by others.

Copyright-Notice: (c) Copyright 1996-1998 by Consensus Development Corporation -- All Rights Reserved

    ********************************************************************* 
    Due to the November 15, 1998 dissolution of the SSL-Talk mailing 
    list, this will be the last version of this FAQ in its current form. 
    It will be replaced by a more general TLS & SSL FAQ in the near 
    future that is not tied to any mailing list or newsgroup. 
    *********************************************************************

All information contained in this work is provided "as is." All warranties, expressed, implied or statutory, concerning the accuracy of the information of the suitability for any particular use are hereby specifically disclaimed. While every effort has been taken to ensure the accuracy of the information contained in this work, the authors assume(s) no responsibility for errors or omissions or for damages resulting from the use of the information contained herein.

This work may be copied in any printed or electronic form for non-commercial, personal, or educational purposes if the work is not modified in any way, provided that the copyright notice, the notices of any other author included in this work, and this copyright agreement appear on all copies.

Consensus Development Corporation also grants permission to distribute this work in electronic form over computer networks for other purposes, provided that, in addition to the terms and restrictions set forth above, Consensus Development Corporation and/or other cited authors are notified and that no fees are charged for access to the information in excess of normal online charges that are required for such distribution.

This work may also be mentioned, cited, referred to or described (but not copied or distributed, except as authorized above) in printed publications, on-line services, other electronic communications media, and otherwise, provided that Consensus Development Corporation and any other cited author receives appropriate attribution.

Comments about, suggestions about, or corrections to this document are welcomed. If you would like to ask us to change this document in some way, the method we appreciate most is for you to actually make the desired modifications to a copy of the posting, and then to send us the modified document, or a context diff between the posted version and your modified version (if you do the latter, make sure to include in your mail the "Version:" line from the posted version). Submitting changes in this way makes dealing with them easier for us and helps to avoid misunderstandings about what you are suggesting.

Many people have in the past provided feedback and corrections; we thank them for their input.

In particular, many thanks to:

Christopher Allen ChristopherA@consensus.com
Shannon Appel SAppel@consensus.com
Nelson Bolyard NelsonB@netscape.com
Tim Dierks TimD@consensus.com
Eric Greenberg ericg@netscape.com
Charles Neerdaels chuckn@netscape.com
Bruce Schneier schneier@counterpane.com
Tom Weinstein tomw@netscape.com
Jonathan Zamick JonathanZ@consensus.com

Remaining ambiguities, errors, and difficult-to-read passages are not their fault. :)

-1.1) What is the SSL-Talk List?
The SSL-Talk List was an email list intended for discussion of ...
-1.1.1) Do archives of the SSL-Talk List exist?
Yes. An archive is maintained at: ...
-1.2) What is SSL?
SSL is the Secure Sockets Layer protocol. Version 2.0 originated ...
-1.2.1) What is TLS?
TLS is the Transport Layer Security protocol. It is effectively SSL ...
-1.3) Has netscape replaced the SSL-Talk mailing list?
Yes. Netscape, the host of the old ssl-talk mailing list, has ...
-1.4) Are there any other SSL mailing lists?
Some people prefer mailing lists to newsgroups. Fortunately, several ...
-2.1) What is the current version of the SSL protocol?
The current version is SSL 3.0, as documented ...
-2.2) Where can I get a "management overview" of SSL and web security?
There is a brief introduction on how Netscape uses public ...
-2.3) Where can I get a more in-depth look at SSL and web security?
The online version of the technical specifications for the SSL 3....
-2.4) What software supports SSL 2.0 and SSL 3.0?
A list of web servers that support SSL 3.0 can be found using the ...
-2.5) What are the laws regarding the import and export of cryptography in various countries?
There is an impressive International Law Crypto Survey ...
-3.1) What is a proxy server?
A proxy server is a computer program that resides on your ...
-3.2) How does SSL work through (application level) firewalls, gateways and proxy servers?
SSL was designed to provide security between client and server ...
-3.3) Since SSL is supposed to withstand replay attacks, does this preclude proxy servers from caching the data?
A proxy server must pass SSL directly through without caching....
-3.4) What ports does SSL use?
Theoretically SSL can transparently secure any TCP-based ...
-3.5) Do you have any information on sftp?
SSL FTP has been assigned port 990 under the name ftps....
-4.1) Does SSL protect users from replay attack by eavesdroppers or message interceptors?
Yes. The client and the server each provide part of the random ...
-4.2) Isn't encrypt-only SSL open to "man-in-the-middle" attacks?
Yes, even though SSL 3.0 defines an encrypt-only cipher suite (...
-4.3) When did MD5 get "disavowed"?
It hasn't been truly disavowed, but weaknesses have ...
-4.4) The record protocol sits underneath the other protocols, right?... (SSL)
... It appears that information can be sent only in blocks. ...
-4.5) It appears that there is no way in the SSL protocol to resynchronize blocks if they get out of synch. Is that true?
Yes. SSL relies on an underlying reliable protocol to assure ...
-4.6) Why does SSL3 have Diffie-Hellman encryption at all? What good is it?...
...Exchanging random numbers that are encrypted with the server's (...
-4.7) What is TLS? What happened at these meetings? Has anything come out of them yet?
TLS is the Transport Layer Security Working Group of the ...
-4.8) What is the purpose of pad1 and pad2, and why were the numbers 0x36 and 0x5c chosen? (SSL)
The purpose of the construction of a keyed-MAC in the form ...
-4.9) Are you aware of any SSL toolkits supporting client authentication?
SSLRef 3.0 and SSL Plus both support SSL 3.0 client authentication. ...
-4.10) What SSL implementations should I test against?
There is no formal conformance testing, but Netscape does ...
-4.11) What is the difference between SSL 2.0 and 3.0?
Security improvements:...
-5.1) How does Netscape handle client certificates in Communicator 4.X? Navigator 3.X?
Netscape describes their framework for web-based key generation ...
-5.2) What is the format of the SSL certificates used by Netscape Navigator?
Netscape has documented their SSL 2.0 certificate format ...
-5.3) I am distributing load on several different web servers and I don't want to have to have a different certificate for each. How can I do this?
When establishing a secure connection in SSL, many SSL ...
-5.4) When comparing a URL against the common name of the certificate, why don't you do a reverse-DNS lookup?
DNS is not a secure name service, and trying to treat it like ...
-5.5) Does Netscape require hierarchical naming (that is, distinguished names) for its certificates?
Yes, Netscape requires distinguished names....
-5.6) Where can I get more information on certificates?
PKIX is an IETF working group dedicated to providing standards ...
-5.7) What other CAs exist besides VeriSign?
We know of these CAs:...
-5.8) How do I set up my own Certificate Authority?
There is some support for creating your own CA in SSLeay; there ...
-5.9) What criteria should I use in deciding between one CA and another?
The purpose of a Certificate Authority is to bind a public key ...
-5.10) What are Attribute Certificates?
Attribute Certificates are a new type of certificate proposed ...
-6.1.1) I just downloaded a new version of Netscape's browser, and it doesn't have 128-bit encryption. What version(s) of the browser have 128-bit encryption?
This is not an official statement by Netscape, and Netscape has not ...
-6.1.2) I just downloaded a newly released version of Netscape's browser and my bank's server tells me my browser does not have adequate security. What's wrong?
Here are the likely explanations for this:...
-6.1.3) I downloaded a version of Netscape's browser that is newer than version 4.05. Now, when I go to certain https web sites that used to work for me (like my bank) I get an error message telling me that "Netscape has received bad data from the server." I've been told the problem is with SSL v3 in my new browser, and that I should disable SSL v3 in my browser. What's wrong with SSL v3 in these new browsers? Should I disable it?
Newer versions of Netscape's browsers enforce the legal export ...
-6.1.4) Do Netscape's browsers cache data on disk that has been received via https?
Navigator 3.0 and Communicator 4.x have an option to allow on-...
-6.1.5) Is the cached data encrypted using some key? (Netscape SSL implementation issues)
No, Navigator and Communicator do not encrypt documents that are ...
-6.1.6) Does Netscape use "regular" RSA libraries (such as BSAFE) or "custom" RSA code? More specifically, is Netscape using BSAFE 3.0?
Netscape is a BSAFE source licensee. Much of the code in BSAFE 3.0 ...
-6.1.7) Are the 512-bit RSA keys used by exportable servers generated on the fly by Netscape's servers? How often are they changed? Does the Netscape server take care of changing them automatically? (Netscape SSL implementation issues)
In Netscape's server products, if the server's public key is longer ...
-6.1.8) How can additional root CA certificates be added to the browser's certificate database? (Netscape SSL implementation issues)
Root keys for CA (Certificate Authority) certificates may be ...
-6.1.9) What X.509v3 certificate extensions are supported by the various versions of Netscape browsers?
Please see ....
-6.1.10) The Help Information for Netscape's Enterprise server indicates that the server supports 6 ciphers for SSL 2.0 and 6 ciphers for SSL 3.0...
...However, the Encryption|Security Preferences menu in the ...
-6.1.11) When will Netscape support SSL sockets for Java browser applets?
There are presently no announced plans to do so....
-6.2.1) Which of Microsoft's products will support SSL?
The text for sub-section 6.2 was grabbed from various ...
-6.2.2) Which Microsoft products support Client Authentication?
Client authentication as implemented by Microsoft Internet ...
-7.1.1) What is SSLRef 3.0?
This subsection contains information on SSLRef 3.0 which ...
-7.1.2) How can I license SSLRef 3.0? What does it cost? With whatrestrictions?
The SSLRef 3.0 distribution includes a license for non-...
-7.2.1) What is the relationship between SSLRef and SSL Plus?
This sub-section contains information specific to the SSL Plus: ...
-7.2.2) What is the relationship between SSL Plus and SSLRef 2.0?
There is no relationship between SSLRef 2.0 and SSL Plus -- SSL ...
-7.2.3) How can I license SSL Plus?
SSL Plus is available for commercial use only. Certicom will work ...
-7.2.4) Is there any relationship between SSL Plus and Winsock 1.1 or Winsock 2.0?...
...Which Winsock would you recommend using to test ...
-7.2.5) How does the data flow within the application, WinSock, SSL, TCP/IP stack layers?
The short answer is that you insert SSL Plus between your I/O ...
-7.2.6) With the WinSock 2.0 architecture, the application need only chose an appropriate SSL-enabled service provider. Does SSL Plus support this?
With WinSock 2.0 there is some discussion of functionality that ...
-7.2.7) Does SSL Plus support yielding?
SSL Plus includes support for processor yielding ...
-7.2.8) I don't understand the nomenclatures of constants such as "SSL_RSA_EXPORT_WITH_RC4_40_MD5" -- where are they defined?
They are actually defined by the SSL 3.0 specification, but also see ...
-7.2.9) In what order are the cipher suites called? (SSL Plus)
The default order of the cipher suites is:...
-7.2.10) Can I change the order of the cipher suites? (SSL Plus)
Yes. This is easily done with the SSLSetCipherSuites function....
-7.2.11) Does SSL Plus support compression?
Not as of 2.0. If there is a specific customer requirement, or if a ...
-7.2.12) In the function SSLWriteRecord(), the data buffer is copied, encrypted, then enqueued on the SSL write queue. The function then returns. What thread services the write queue? How is the thread created? (SSL Plus)
The write queue is serviced by the public function ...
-7.2.13) When I call SSLRead(), on returning, the length argument should be replaced with the number of bytes actually read. In practice, this doesn't seem to be happening. What am I doing wrong? (SSL Plus)
The difficulty is that it's hard for SSL to precisely emulate ...
-7.2.14) If session cache is stored in a database, can multiple Unix processes share the same session data? (SSL Plus)
There is no information stored in the session database which can'...
-7.3.1) Where is the SSLeay FAQ?
This sub-section contains information specific to the ...









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