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I SHALL DEVOUR YOUR HEART AND FEAST ON YOUR SOUL (so don't bug me).


1d
comment Known characters in passwords?
Honestly, I don't need the tell-tale '==' signs to recognize 'gorv/cp+lSiwiEfKck2dVg' as some Base64 encoding.
2d
comment XTS vs AES-CBC with ESSIV for file-based filesystem encryption
GnuPG's better encryption comes from the fact that it processes the whole file in one go, with a fresh random IV. All the difficulty of FDE is that it tries to support efficient updates, where only the data chunks that are updated get reencrypted. In the file-on-Dropbox case, the encryption should really occur when uploading the filesystem image, not for each file write.
2d
comment XTS vs AES-CBC with ESSIV for file-based filesystem encryption
If you put the encrypted filesystem only once, then there is no problem. Just do it. Potential vulnerabilities begin to occur if you then retrieve the filesystem, modify it, then put it back on Dropbox: the successive versions become visible to attackers. What you can do is to take a filesystem image (not necessarily encrypted with anything), then encrypt it with GnuPG before upload, and decrypting it when downloading it. This will be stronger, both against passive and active attackers.
2d
comment EAP-TLS fragmentation implementation
For the CertificateVerify, you must hash all previous messages, so ClientHello, ServerHello, Certificate (from server), ServerKeyExchange, CertificateRequest, ServerHelloDone, Certificate (the one from the client) and ClientKeyExchange.
Jul
24
comment Can any ECC field element be safely serialized as “compressed” and then restored as uncompressed?
Usually, in crypto, we use finite groups and rings and fields, where there is no notion of negative at all, since there is no natural ordering of elements (you cannot have a "less than" relationship compatible with the group law on a finite group).
Jul
24
comment GPG encryption and signing
Yes, with --sign you sign but you do not encrypt. Distinct operations. The --armor is not about encryption (as in: hiding information from people who don't know some specific key) but about surviving alterations in transit (as in: some email server will convert LF end-of-line characters to CR+LF, or will replace what it supposes to be an "unprintable character" with a "?"). The "armoring" is about coping with the careless way email servers handle emails. On a similar note, Base64 is also internally used when you send a binary attachment, for pretty much the same reason.
Jul
22
comment Broadband security question
You don't get downvoted when you are not trusted; you get downvoted when your questions or answers are poorly written, off-topic, or just plain wrong.
Jul
22
comment Identifying suspicious encrypted traffic
It is good that Google uses TLS when they try to get new software version or to retrieve information about your Google+ account or anything like that. Otherwise it could be spied upon or altered by attackers. You should rejoice that such traffic is "encrypted". As for the port number, it does not really matter; in fact, using port 443 would be confusing if that which goes inside the TLS is not HTTP.
Jul
18
comment Are files hosted on cloud servers/websites/databases manually checked by people?
Password protection on file storage system is just an access control; the files still are there, ready to be read by any sysadmin on the server side. If you want a storage system where the sysadmins cannot read files, then the files must be encrypted on the client computer with a password or key that never goes to the server.
Jul
18
comment What is the collision likelihood of MD5 when non-numeric values are removed?
I don't know enough of your context to emit any recommendation. I suppose that you are trying, from a smartphone app, to obtain a kind of smartphone identifier that you wish to upload to a server of yours in order to recognize phones from each other. In that case, it seems to me that any attempt at anonymizing is hopeless, regardless of the function you use, basically because the phone can compute that function.
Jul
18
comment Is using a CA more secure if I'm self-signing anyway?
The CA private key is needed on the machine which issues certificates; that needs not be the same as the SSL server. In particular, the CA can be an offline machine. What the SSL server needs is the private key for the SSL server's own certificate. Having a separate CA allows for easier damage containment in case of compromise of the SSL server (if the CA is offline, it is assumed that it cannot be compromised remotely).
Jul
13
comment Why enable SMTP STARTTLS if OpenSSL is dangerous?
The (RSA) signature must be made anew for each connection, because that which is signed includes the DH public key, but also the client and server "randoms" (from the ClientHello and ServerHello messages), which change for each handshake. However, the DH key can be shared and reused (though the point of DHE is that the DH private key is never saved on a non-volatile medium). Since cost of generating a new DH key pair is similar to that of a RSA signature, and so is finalizing the DH key exchange, making a new key-pair for each handshake would account for at most 1/3rd of total cost.
Jul
13
comment Why enable SMTP STARTTLS if OpenSSL is dangerous?
@supercat: well, you have just described "DHE" cipher suites as commonly used in SSL. With a DHE cipher suite, the server sends a DH public key that the server signs with its "permanent" private key (often some RSA private key). The server can create a new DH key pair for each connection ! It is not very expensive, and clients don't expect the key to stay the same; they don't record it anywhere.
Jul
13
comment Why enable SMTP STARTTLS if OpenSSL is dangerous?
Private key operations take time about 1ms or so (depending on algorithm, key length, type of CPU, clock rate...). Context-switching and sending a short data element (e.g. a hash to be signed, or a signature) between two process on the same machine, or between a process and the kernel, is more a matter of a few micro-seconds, so we are talking about an overhead of less than 1% here, even when the CPU spends most of its time doing asymmetric crypto (which is a DoS situation, not something normal).
Jul
12
comment Why enable SMTP STARTTLS if OpenSSL is dangerous?
The "damage" from Heartbleed was really due to the panic which submerged so many people, rather than a specific technical detail. Yet there is value in isolating private keys out of the process address space. This is why Microsoft is trying to replace their old CryptoAPI with a new API called "CNG", because the latter allows for private keys to be stored in kernel space, thus out of reach of some vulnerabilities (this also prevents the keys from leaking to swap space).
Jul
11
comment Usefulness of bcrypt(UUIDv4())
This might be related to the fact that an UUID is 128 bits, but only 122 are random (the 6 other mostly encode the fact that the UUID is "v4"). In that sense, it "loses" 6 bits (not 4) or randomness. But that's hardly an issue -- 122 bits are still a lot more than is needed to defeat exhaustive search.
Jul
11
comment Would it be secure to generate random number using AES?
When /dev/urandom is not a good source of randomness on a given machine, nothing else is.
Jul
10
comment What are the alternatives to ECDSA for an authentication protocol?
@user49555: at least libgcrypt implements RFC 6979 since version 1.6.0 (released on December 2013).
Jun
24
comment How can PayPal spoof emails so easily to say it comes from someone else?
Also, I am not a native English speaker.
Jun
24
comment How can PayPal spoof emails so easily to say it comes from someone else?
Dear @HelloWorld, poetry has been a widespread method to convey elaborate ideas since the Epic of Gilgamesh, about 4000 years ago. Confucius used poetry. The Odyssey is a famous poem full of philosophical content. It would be a shame if poetry became suddenly unacceptable. In fact, newbies (and seasoned users) should strive to learn to express their ideas elegantly.