# Key Sets and Wildcards

For every individual position within a character string, an OCVMax tool uses a key set to specify the individual characters it expects to verify. A character string of 10 characters, for example, uses 10 key sets.

For character strings that remain constant, each key set contains a single character key. When you want to verify a character string where one or more character keys at a specific position can vary between run-time images, you must create a key set with wildcards, or multiple character keys. For example, the following figure shows three character strings that can all be verified with the same OCVMax tool, since the key set at the last position has been configured with all digit characters:

Be aware that specifying a mix of wildcard characters that contain both blank and non-blank characters is not recommended and can seriously impact the performance of an OCVMax tool.

See the following sections for more information: