FAQ

OpenSSL  -  Frequently Asked Questions
--------------------------------------

* Where is the documentation?
* How can I contact the OpenSSL developers?
* Do I need patent licenses to use OpenSSL?
* Is OpenSSL thread-safe?
* Why do I get a "PRNG not seeded" error message?


* Where is the documentation?

OpenSSL is a library that provides cryptographic functionality to
applications such as secure web servers.  Be sure to read the
documentation of the application you want to use.  The INSTALL file
explains how to install this library.

OpenSSL includes a command line utility that can be used to perform a
variety of cryptographic functions.  It is described in the openssl(1)
manpage.  Documentation for developers is currently being written.  A
few manual pages already are available; overviews over libcrypto and
libssl are given in the crypto(3) and ssl(3) manpages.

The OpenSSL manpages are installed in /usr/local/ssl/man/ (or a
different directory if you specified one as described in INSTALL).
In addition, you can read the most current versions at
<URL: http://www.openssl.org/docs/>.

For information on parts of libcrypto that are not yet documented, you
might want to read Ariel Glenn's documentation on SSLeay 0.9, OpenSSL's
predecessor, at <URL: http://www.columbia.edu/~ariel/ssleay/>.  Much
of this still applies to OpenSSL.

The original SSLeay documentation is included in OpenSSL as
doc/ssleay.txt.  It may be useful when none of the other ressources
help, but please note that it reflects the obsolete version SSLeay
0.6.6.


* How can I contact the OpenSSL developers?

The README file describes how to submit bug reports and patches to
OpenSSL.  Information on the OpenSSL mailing lists is available from
<URL: http://www.openssl.org>.


* Do I need patent licenses to use OpenSSL?

The patents section of the README file lists patents that may apply to
you if you want to use OpenSSL.  For information on intellectual
property rights, please consult a lawyer.  The OpenSSL team does not
offer legal advice.

You can configure OpenSSL so as not to use RC5 and IDEA by using
 ./config no-rc5 no-idea

Until the RSA patent expires, U.S. users may want to use
 ./config no-rc5 no-idea no-rsa

Please note that you will *not* be able to communicate with most of
the popular web browsers without RSA support.


* Is OpenSSL thread-safe?

Yes.  On Windows and many Unix systems, OpenSSL automatically uses the
multi-threaded versions of the standard libraries.  If your platform
is not one of these, consult the INSTALL file.

Multi-threaded applications must provide two callback functions to
OpenSSL.  This is described in the threads(3) manpage.


* Why do I get a "PRNG not seeded" error message?

Cryptographic software needs a source of unpredictable data to work
correctly.  Many open source operating systems provide a "randomness
device" that serves this purpose.  On other systems, applications have
to call the RAND_add() or RAND_seed() function with appropriate data
before generating keys or performing public key encryption.

Some broken applications do not do this.  As of version 0.9.5, the
OpenSSL functions that need randomness report an error if the random
number generator has not been seeded with at least 128 bits of
randomness.  If this error occurs, please contact the author of the
application you are using.  It is likely that it never worked
correctly.  OpenSSL 0.9.5 makes the error visible by refusing to
perform potentially insecure encryption.