15. An apparatus for verifying a document belonging to a particular class of documents, said particular class being one of a plurality of classes of document, each of said classes corresponding to a class encryption/decryption key pair CE,CD, said document incorporating encrypted information E comprising information M derived from said document and encrypted with an encryption key E selected from an encryption/decryption key pair E, D and said document further incorporating encrypted decryption, key CE comprising decryption key D for said key pair E, D encrypted with encryption key CE selected from class encryption/decryption key pair CE, CD associated with said particular class, comprising: a) means for scanning said document to input scanned information, said scanned information including said encrypted information E, said encrypted decryption key CE, and information identifying said particular class; b) means responsive to enabling information for enabling retrieval of a decryption key from any document in a selected group of said classes of documents and responsive said identifying information to determine if said document is in said selected group, and if so retrieving said decryption key D from said scanned information; c) means for decrypting said encrypted information E from said scanned information to obtain decrypted encrypted information D; and d) means for comparing said decrypted encrypted information D with said information M to verifying the information contained in said document as authentic and unchanged.
15. An apparatus for verifying a document belonging to a particular class of documents, said particular class being one of a plurality of classes of document, each of said classes corresponding to a class encryption/decryption key pair CE,CD, said document incorporating encrypted information E comprising information M derived from said document and encrypted with an encryption key E selected from an encryption/decryption key pair E, D and said document further incorporating encrypted decryption, key CE comprising decryption key D for said key pair E, D encrypted with encryption key CE selected from class encryption/decryption key pair CE, CD associated with said particular class, comprising: a) means for scanning said document to input scanned information, said scanned information including said encrypted information E, said encrypted decryption key CE, and information identifying said particular class; b) means responsive to enabling information for enabling retrieval of a decryption key from any document in a selected group of said classes of documents and responsive said identifying information to determine if said document is in said selected group, and if so retrieving said decryption key D from said scanned information; c) means for decrypting said encrypted information E from said scanned information to obtain decrypted encrypted information D; and d) means for comparing said decrypted encrypted information D with said information M to verifying the information contained in said document as authentic and unchanged. 16. An apparatus as described in claim 15 wherein said enabling means further comprises memory means for storing preselected keys CD, said preselected keys CD having a one-to-one correspondence with said classes, and wherein said enabling means responds to said enabling information to enable access to a group of said preselected keys CD, said group of keys corresponding to said group of classes.