WHAT VERSION OF OPENSSL?
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OpenSSL 0.9.6 is supported but some functionality requires 0.9.7 or greater.

KEYS MANAGER
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OpenSSL does not have a keys or certificates storage implementation. The
default xmlsec-openssl key manager uses a simple keys store from xmlsec
core library based on plain keys list. Trusted/untrusted certificates
are stored in STACK_OF(X509) structures.

KNOWN ISSUES.
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1) One day we might decide to drop OpenSSL 0.9.6 supprot and remove all
these ifdef's to simplify the code.