1. A method for generating a conditional electronic signature, performed in response to one or more conditions being specified for an electronic signature of a data item, the method comprising: hashing the data item to generate a digest of the data item; hashing each condition of the one or more conditions separately from each other and separately from the data item to generate one or more condition digests respectively corresponding to the one or more conditions; setting a reference digest equal to the digest of the data item; a computer iteratively processing a unique condition digest of the one or more condition digests in each iteration of a loop for a sufficient number of iterations to process all of said condition digests, said processing in each iteration comprising concatenating the reference digest with the unique condition digest of the iteration to generate a concatenand and hashing the concatenand to generate a hashed concatenand that serves as the reference digest for the next iteration if the next iteration is performed, each unique condition digest being a different condition digest in each iteration of the loop, the regenerated reference digest of the last iteration of the loop being a last digest; and encrypting the last digest to generate a digital signature block that represents the data item and the one or more conditions and enables cryptographic verification of both the data item and the one or more conditions, said encrypting comprising signing the last digest with a digital signature, wherein the one or more conditions is a plurality of conditions.