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Ardi does not obtain his private key from the PKI. The PKI obtains Ardi's public key from Ardi. Ardi owns a public/private key pair: a public key and a private key that "dance together" (they are two mathematical facets of a single object). The public key is meant to be public. The job of the PKI is to publish the public key, and offers some verifiable ...


5

Your description is a bit confused and appears to be wrong. In particular, we see Alice computing here Diffie-Hellman half gKA and then proceed to send... her Diffie-Hellman secret KA to Bob, which is not at all what she should do. Plain Diffie-Hellman works the following way: Alice generates (randomly) her secret KA and computes gKA. Bob generates ...


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This is done as you say, except with an optimization. The email itself is encrypted with a newly generated random symmetric key; and that key is then encrypted with the public key of each recipient. This means that if you have a 2MB email and send it to 20 people, total size is a bit more than 2MB, not 40MB.


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Advantage of Using Subkeys Using subkeys has the main advantage that in case you have to revoke them, you're not losing all reputation in the web of trust do not have to exchange new keys with other participants you're communicating with. For example, if you stored your subkeys (and your public primary key, not your secret primary key!) on a mobile phone ...


3

The option names are not part of the SSH protocol; they are specific to a given implementation. I suppose you are talking about OpenSSH. As per the documentation: RSAAuthentication Specifies whether pure RSA authentication is allowed. The default is “yes”. This option applies to protocol version 1 only. So this does not apply to your case, ...


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If you only check that the certificate is valid in the PKI, but not that it matches the server name (either the domain or IP address), then you can be fooled by a certificate issued to a different site. Suppose: I own malicioussoftware.com Thus I can but a certificate for malicioussoftware.com You (attempt to) connect to https://www.microsoft.com, but I ...


1

A key is a key. There is no such thing as a "RSA-with-SHA-1 key". A RSA key that can be used for signatures (using the PKCS#1 standard) will be used in conjunction with some other parameters, including a hash function such as SHA-1 and SHA-256; but there is no intrinsic property of a key that would prevent usage of SHA-1 or SHA-256 as hash function within a ...


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This is a security feature called certificate pinning (or public key pinning). In this case the browser knows which certificate (or public key) to expect and refuses any attempts to override it by the user. Twitter is included for public key pinning since Firefox 32. See https://wiki.mozilla.org/SecurityEngineering/Public_Key_Pinning for more details.


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Usually when generating keyrings the program will generate both an encryption key and a signature key in the public keyring. If you run gpg --edit-key KEYID it will probably show usage: SC and usage: E for your key and subkey respectively.



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