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33

Encryption provides confidentiality, i.e. ensures that only intended recipient will be able to decrypt the message. Signing provides authentication, i.e. allows recipient to check that message was sent by a particular sender and wasn't modified. One way to look at this in the context of PKI is like this: encryption only requires the knowledge of ...


9

Encryption with someones public key provides confidentiality, but doesn't provide authentication or integrity. In a PKI architecture, you encrypt your message with the public key of the recipient. This proves only that you know their public key, but nothing about yourself. When their public key is indeed public, you could be anyone, including an attacker ...


4

If I left a locked box on your porch in the middle of the night and chained it to your door and dropped a key in the mail slot, it would be secure. Nobody else would be able to get in to it and only you would be able to open it, but you would have no way to know who left it for you. It could have been left by the Publisher's Clearing House prize guy or a ...


4

Sign Your License File You want to sign the data with your private key to create a signature. Generate a license file Encrypt the file with your private key (signing it). Provide the public key with your application In your program, decrypt and verify the file contents have not changed with your public key. The signature cannot be replaced since only ...


3

Yes, the same RSA key pair can be used for both (Open)SSL and OpenPGP/GnuPG. The monkeysphere project contains a tool to convert RSA keys in PEM format to the one defined by OpenPGP, pem2openpgp. For converting the SSH key pair into the PEM format, there already is a comprehensive answer in Converting keys between openssl and openssh.


3

What the page you link to means is that there are known attacks which, when implemented, would allow building collisions with some costs: If the goal is "raw collisions" then the computational effort is equivalent to running 261 times the SHA-1 function. A raw collision is such that the attack produces two messages m and m' which are distinct but hash to ...


3

SHA1 hash has 160bits. If SHA1 was safe, you would need approximately 2^80 iterations to find a collision. Why 2^80 and not 2^160? Because of birthday paradox: http://en.wikipedia.org/wiki/Birthday_attack The general "collision finding" algorithm works like this: http://en.wikipedia.org/wiki/Cycle_detection#Tortoise_and_hare ...simply, to rabbits, one is ...


2

PGP Format Versions and Key IDs Older versions of the PGP Key Format have several issues that potentially harm security. RFC 4880 further explains these, summarized very briefly: higher chances for key ID collisions fingerprint only hashes key, not size and algorithm (again, higher chance for ID collisions) use of MD5, which is considered broken Anyway, ...


2

This highly depends on the smart card. Some card simply provide a key store whereas others provide a complete infrastructure where you send your data and the smart card can sign and/or encrypt the data. The second type (which is typically meant when using the term smart card) have the advantage that the (private) keys never leave the smart card.


2

Do GPG/PGP keyservers "garbage collect" old keys which have expired, been revoked, or simply haven't been updated in a decade? A kind of "garbage collection" might theoretically be implemented for some OpenPGP key servers, but currently isn't (at least not for the large pool of synchronizing key servers). There are several reasons: Sharing ...


1

Yes, you can buy one certificate and use it on unlimited number of servers. However, some servers may require you to convert the certificate and the private key into an appropriate format. You may look into documentation to find the details for each program.


1

The way I look at it is that if I have an encrypted message which is a series of bytes I can decrypt this with your public key. However any series of bytes is "valid" as a result of your encryption. This means that if somebody modifies the message then I can still decrypt it, I just won't get what you originally encrypted. The person who did the tampering ...


1

Lets assume that we're talking about PGP/GPG keys, and you've uploaded your public key for signing to one of the main PGP/GPG key servers. If you're curious how to revoke a certificate, here's a Guide to Revoking PGP/GPG Certificates. With those assumptions in mind: Will all things I have signed in the past with those subkeys be considered ...


1

Like this: CA machine: ca.crt, ca.key Server: ca.crt, server.crt, server.key Clients: client.crt, client.key, ca.crt Notably, ca.key does NOT go on the server. If the server is compromised, then the attacker won't get ca.key. With easy-rsa you generate the key and certicate on the CA machine, and send them to the client. Technically you don't need to ...


1

Yes, it matters when: 1) there is a constrained hardware and there are constrains on the time that it takes to run the whole operation (protocol) that includes authentication/encryption (e.g., waving a smartcard at a tourniquet when paying for entering a metro). The operation might include several encryption and decryption operations that take place in the ...


1

By default, a user’s SSH keys are stored in that user’s ~/.ssh directory. You can check if your private key is in that directory by listing the contents: $ cd ~/.ssh $ ls authorized_keys2 id_dsa known_hosts config id_dsa.pub The private key is usually something like id_dsa or id_rsa. To regenerate the public key part with just a private ...


1

The «reference browsers» are marked with an R in the table below. What results were you given there? The problem may be on some of them (IE?) not supporting those ECDHE_RSA_* ciphers.



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