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Trim the lead some more to keep it less redundant, less fixated on just encryption, and more to the point. |
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|pages=283–319
|access-date=2022-10-08
}}</ref><p>For example, a journalist can publish the public key of an encryption key pair on a web site so that sources can send secret messages to the news organization in ciphertext.</p><p>Only the journalist who knows the corresponding private key can decrypt the ciphertexts to obtain the sources' messages—an eavesdropper reading email on its way to the journalist cannot decrypt the ciphertexts. However, public-key encryption does not conceal [[metadata]] like what computer a source used to send a message, when they sent it, or how long it is.<ref name="dds2009anoncomm">{{cite book
|editor-last=Rosenberg
|editor-first=Burton
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|url=https://eprint.iacr.org/2001/079
|access-date=2024-11-24
}}</ref>—it just conceals the content of the message.</p>
* In a '''[[digital signature]]''' system, a sender can use a private key together with a message to create a '''signature'''. Anyone with the corresponding public key can verify whether the signature matches the message, but a forger who does not know the private key cannot find any message/signature pair that will pass verification with the public key.<ref name="hac-digsig">
{{cite book
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|archive-url=https://web.archive.org/web/20220420003617/https://cseweb.ucsd.edu/~mihir/papers/gb.pdf#page=168
|url-status=live
}}</ref><p>For example, a software publisher can create a signature key pair and include the public key in software installed on computers. Later, the publisher can distribute an update to the software signed using the private key, and any computer receiving an update can confirm it is genuine by verifying the signature using the public key. As long as the software publisher keeps the private key secret, even if a forger can distribute malicious updates to computers, they cannot convince the computers that any malicious updates are genuine.</p>
One important issue is confidence/proof that a particular public key is authentic, i.e. that it is correct and belongs to the person or entity claimed, and has not been tampered with or replaced by some (perhaps malicious) third party. There are several possible approaches, including:
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