Source verification using images

Original source verifying data defining a first source verifying image are stored in memory. The first source verifying image can be produced by a human making marks by hand in a field of a form, which can then be provided by a scanner or a facsimile transmission through image input circuitry. If a second source verifying image is received that is the same as the first source verifying image, an operation is performed that would not be performed if the images were not the same, such as an operation accessing a related item of data. For example, the first source verifying image can be received with a document image, and data defining the document image and the original source verifying data can be stored so that a source verifying image that is the same as the first source verifying image must be received before an operation can access the document data and provide it to image output circuitry for printing or facsimile transmission. As a result, the marked form is analogous to a key: Only someone who possesses the marked form or a high quality copy can obtain access to the document data. If the marked form is lost or destroyed, the document data cannot be accessed.