Values of this type denote a credential value, e.g. an encrypted password.
All printable characters are allowed. Since a credential contains some kind of secret, the sequence of characters might have some hidden syntax to be interpreted by other parts of Zettelstore.
A credential never compares to any other value. A comparison will never match in any way.
If a list of zettel should be sorted based on a credential value, the identifier of the respective zettel is used instead.