1. A computer-implemented method comprising: appending, to a data structure of an electronic document having at least a first digital signature and a first piece of collateral information stored therein, a second digital signature when connectivity to a certificate authority is unavailable, wherein the first piece of collateral information includes validation-related information for validating the first digital signature and is stored in a repository of collateral information operable to validate at least the first digital signature; based on the second digital signature having been appended when connectivity to the certificate authority was unavailable, retrieving a second piece of collateral information from the certificate authority when connectivity thereto is available, the second piece of collateral information including validation-related information for validating the second digital signature; determining that at least a portion of the second piece of collateral information is not included in the repository of collateral information; in accordance with determining that the at least a portion of the second piece of collateral information is not included in the repository of collateral information, adding at least the portion of the second piece of collateral information to the repository of collateral information; and storing the repository of collateral information with the electronic document in a memory storage location, the repository of collateral information being stored separate from the digital signatures within the data structure of the electronic document and operable to validate at least the first and second digital signatures.