A digital signature in electronic exchange of information provides the same kind of facilities that are expected from a handwritten signature in paper-based mail. Hence it is applicable to providing entity authentication, data origin authentication, non-repudiation, and integrity of data. Specifies six digital signature schemes giving data recovery: NR, ECNR, ECMR, ECAO, ECPV, and ECKNR. NR is defined on a prime field; ECNR, ECMR, ECAO, ECPV, and ECKNR are defined on an elliptic curve over a finite field.