A digital signature in software has about the same role as a real signature on a document. It proves that a certain person has signed the document thereby authenticating it. A signature increases security around a document for both parties involved, i.e. the one who signed the document – the signee – and the one that uses the document afterwards. The one who signed can claim that the document belongs to them, i.e. it originates from them and cannot be used by another person. If you sign a bank loan request then you should receive the loan and not someone else. Also, the party that takes the document for further processing can be sure that it really originates from the person who signed it. The signee cannot claim that the signature belongs to some other person and they have nothing to do with the document. This latter is called non-repudiation. The signee cannot deny that the document originates from him or her.
Digital signatures in software are used to enhance messaging security. The receiver must be able to know for sure that the message originated with one specific sender and that the sender cannot claim that it was someone else who sent the message. While it is quite possible to copy someone’s signature on a paper document it is much harder to forge a strong digital signature.
In this post we’ll review how digital signatures are implemented in .NET
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