Like all popular web browsers, Mozilla Firefox allows you to optionally cache
passwords used for site logins. Site credentials are cached on disk, and in
plaintext by default. However, Firefox allows you to optionally configure a
"Master Password". This password (or passphrase) is used to encrypt the on-disk
cached site credentials, functioning effectively the same way that a keyring
provider and associated passphrase would work. Firefox will challenge the user
for the master password the first time it needs to consult its credentials
cache, and will leave the cache "unlocked" for the duration of the application's
Subversion should be able to do something similar, allowing users to optionally
employ a master passphrase which is used to encrypt and decrypt other sensitive
information stored in its authentication credential cache(s).
See http://wiki.apache.org/subversion/MasterPassphrase for design thoughts.