hash digital signature

what is digital signature is all about?
im do’n a presentation about digital signature 4m an info security point of view so tell me wat is the main things to mention in this presentation i’ve already mentioned the hash function so wat else??
This is it, get all u need in this link below
http://www.pki.gov.kz/cms?host=en-ekey&path=/services/ekeyforprotection
Additionally u could mention the below.
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.
ISO/IEC 9796-3:2006 specifies digital signature mechanisms giving partial or total message recovery aiming at reducing storage and transmission overhead.
ISO/IEC 9796-3:2006 specifies mechanisms based on the discrete logarithm problem of a finite field or an elliptic curve over a finite field.
ISO/IEC 9796-3:2006 defines types of redundancy: natural redundancy, added redundancy, or both.
ISO/IEC 9796-3:2006 gives the general model for digital signatures giving partial or total message recovery aiming at reducing storage and transmission overhead.
ISO/IEC 9796-3:2006 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.
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