Digital signature: Difference between revisions
Jump to navigation
Jump to search
imported>Sandy Harris (new page, basic info, some links) |
imported>Sandy Harris No edit summary |
||
(10 intermediate revisions by 2 users not shown) | |||
Line 1: | Line 1: | ||
{{subpages}} | |||
{{TOC|right}} | |||
'''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. | ||
Line 5: | Line 7: | ||
The steps for the sender are as follows: | The steps for the sender are as follows: | ||
* calculate a hash or [[message digest]] from the message | * calculate a hash or [[message digest]] from the message | ||
* encrypt that hash with the sender's private key | * encrypt that hash with the sender's private key | ||
* | * combine the encrypted hash with information identifying the signer | ||
* append the combination to the message as a signature | |||
Steps for the receiver are: | Steps for the receiver are: | ||
* obtain the sender's public key and | * obtain the sender's public key and authenticate its integrity and source | ||
* decrypt the signature, using the sender's public key, to get the hash value; call it H<sub>1</sub> | * decrypt the signature, using the sender's public key, to get the hash value; call it H<sub>1</sub> | ||
* hash the message body yourself to get another hash value, H<sub>2</sub> | * hash the message body yourself to get another hash value, H<sub>2</sub> | ||
* compare H<sub>1</sub> and H<sub>2</sub> | * compare H<sub>1</sub> and H<sub>2</sub> | ||
* if they are identical, accept the signature as valid | * if they are identical, then you know with overwhelming probability (though not with absolute certainty): | ||
** the documents signed (hash H<sub>1</sub>) and the document received (hash H<sub>2</sub>) are identical (from properties of a [[cryptographic hash]]) | |||
** whoever generated the signature knew the signer's private key (which only the signer should know in a [[public key]] system) | |||
* so you can accept the signature as valid | |||
If both the [[hash (cryptography) | hash]] and the [[public key]] system used are secure, and no-one except the sender knows his private key, then the signatures are trustworthy. | If both the [[hash (cryptography) | hash]] and the [[public key]] system used are secure, and no-one except the sender knows his private key, then the signatures are trustworthy. | ||
The use of digital signatures raises legal issues. There is an online reference <ref>Digital Signature Law Survey https://dsls.rechten.uvt.nl/</ref> for laws around the world. | |||
==References== | |||
{{Reflist|2}} |
Revision as of 23:44, 7 December 2010
![](http://s9.addthis.com/button1-share.gif)
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
- combine the encrypted hash with information identifying the signer
- append the combination to the message as a signature
Steps for the receiver are:
- obtain the sender's public key and authenticate its integrity and source
- 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, then you know with overwhelming probability (though not with absolute certainty):
- the documents signed (hash H1) and the document received (hash H2) are identical (from properties of a cryptographic hash)
- whoever generated the signature knew the signer's private key (which only the signer should know in a public key system)
- so you can 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.
The use of digital signatures raises legal issues. There is an online reference [1] for laws around the world.
References
- ↑ Digital Signature Law Survey https://dsls.rechten.uvt.nl/