Digital signature: Difference between revisions
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'''Digital signatures''' provide [[information security#source authentication|source authentication]] for online documents, messages or records, in a manner analogous to what a signature provides for a paper document. | '''Digital signatures''' provide [[information security#source authentication|source authentication]] for online documents, messages or records, in a manner analogous to what a signature provides for a paper document. | ||
Revision as of 07:40, 10 November 2008
Template:TOC-right Digital signatures provide source authentication for online documents, messages or records, in a manner analogous to what a signature provides for a paper document.
Two cryptographic techniques are used together to produce a digital signature, a cryptographic hash and a public key cryptosystem.
The steps for the sender are as follows:
- calculate a hash or message digest from the message
- encrypt that hash with the sender's private key (which only he should know)
- append the encrypted hash to the message as a signature
Steps for the receiver are:
- obtain the sender's public key and verify its validity
- decrypt the signature, using the sender's public key, to get the hash value; call it H1
- hash the message body yourself to get another hash value, H2
- compare H1 and H2
- if they are identical, accept the signature as valid
If both the hash and the public key system used are secure, and no-one except the sender knows his private key, then the signatures are trustworthy.