Multiple Eyepairs Only is a project to define a file format and to provide tools to use cryptography for things like four-eyes principles. The key idea is this: if information should only be accessible to a group of people together, with the additional possibility to have some redundancy in participants, then MEO is for you.
XCA is an interface for managing RSA and DSA keys, certificates, certificate signing requests, revocation lists and templates. It uses the OpenSSL and Qt4 libraries. Certificates and requests can be created and signed and many x509v3 extensions can be added. XCA supports multiple root and intermediate Certificate authorities. The CAs can be used to create CRLs and extend certificates. The following file-formats are supported: PEM, DER, PKCS#7, PKCS#8, PKCS#10, PKCS#12, and SPKAC.