Skip to main content

encryption - if one doesn't care about protecting a gpg secret key, is it still as secure as using gpg --symmetric?


Each of Alice and Bob is using gpg just to protect his/her own personal files and not using it as a way to send encrypted text to others. Alice has generated a key (gpg --gen-key) that she uses to encrypt/decrypt her personal files (gpg --encrypt --recipient="Alice Personal" alice.secrets.txt and gpg --decrypt alice.secrets.txt.gpg). She knows that in order to read and write to alice.secrets.txt.gpg in her another computer, she needs to export her key (both public key and private key) to her second computer, using commands like:


gpg --armor --export "Alice Personal" > alice.personal.public.key.txt
gpg --armor --export-secret-key "Alice Personal" > alice.personal.private.key.txt

and


gpg --import alice.personal.public.key.txt
gpg --import alice.personal.private.key.txt

So she decides to put her encrypted personal files (alice.secrets.txt.gpg) and her key (alice.personal.public.key.txt and alice.personal.private.key.txt) on a cloud sync service for convenience. Because alice.personal.private.key.txt is on cloud, a third party who may get access to her files on cloud has access to the first of the following two, but not the second.




  • something she has: alice.personal.private.key.txt




  • something she knows: the passphrase to unlock the secret key




She's giving up protecting the first in return for convenience.


On the other hand, Bob uses symmetric encryption to protect his secrets (gpg --symmetric bob.secrets.txt and gpg --decrypt bob.secrets.txt.gpg). He also puts his encrypted personal files on a cloud service. To read and write to bob.secrets.txt.gpg on his another computer, he just needs to successfully recall his passphrase.


Maybe Alice and bob should just use Truecrypt or Boxcryptor. Anyway, question is, are Alice's secrets as safe as Bob's secrets provided that their passphrases are equally good?



Answer



Alice's approach is ever so slightly safer than Bob's. Every encrypted file gets a new symmetric key, which means that:



  • You'll have to break the symmetric key separately for each file instead of once, and those keys are usually easier to break than proper RSA keys (lower key space for higher performance, as we can't lose time with every new message, be it a document or a connection, and RSA doesn't have to be efficient one the key is generated as we usually use it to cypher a symmetric key used for the rest of the document).

  • You might avoid attacks when both the cyphered and uncyphered documents are know. If Eve knows has the original of document and the version encrypted for Alice, it might make it easier to find the key and use it for all other documents.

  • You might avoid attacks made available by knowing many encrypted messages, which could be similar to what we already know with RSA and low exponents.


Comments

Popular Posts

How do I transmit a single hexadecimal value serial data in PuTTY using an Alt code?

I am trying to sent a specific hexadecimal value across a serial COM port using PuTTY. Specifically, I want to send the hex codes 9C, B6, FC, and 8B. I have looked up the Alt codes for these and they are 156, 182, 252, and 139 respectively. However, whenever I input the Alt codes, a preceding hex value of C2 is sent before 9C, B6, and 8B so the values that are sent are C2 9C, C2 B6, and C2 8B. The value for FC is changed to C3 FC. Why are these values being placed before the hex value and why is FC being changed altogether? To me, it seems like there is a problem internally converting the Alt code to hex. Is there a way to directly input hex values without using Alt codes in PuTTY? Answer What you're seeing is just ordinary text character set conversion. As far as PuTTY is concerned, you are typing (and reading) text , not raw binary data, therefore it has to convert the text to bytes in whatever configured character set before sending it over the wire. In other words, when y...

linux - Extract/save a mail attachment using bash

Using normal bash tools (ie, built-ins or commonly-available command-line tools), is it possible, and how to extract/save attachments on emails? For example, say I have a nightly report which arrives via email but is a zip archive of several log files. I want to save all those zips into a backup directory. How would I accomplish that? Answer If you're aiming for portability, beware that there are several different versions of mail(1) and mailx(1) . There's a POSIX mailx command, but with very few requirements. And none of the implementations I have seem to parse attachments anyway. You might have the mpack package . Its munpack command saves all parts of a MIME message into separate files, then all you have to do is save the interesting parts and clean up the rest. There's also metamail . An equivalent of munpack is metamail -wy .

ubuntu - Why does my USB hdd returns SG_IO: bad/missing sense data?

I am able to boot and run commands from external USB hdd; the message in question appears for about 45 seconds then booting continues. GRUB2 is installed on internal HDD. When choosing to boot directly to /dev/sdb the message doesn't appear, however boot time is about the same as booting to internal HDD. /dev/sdb: Timing cached reads: 1018 MB in 2.00 seconds = 508.97 MB/sec Timing buffered disk reads: 80 MB in 3.03 seconds = 26.37 MB/sec pfeiffep@de:~$ sudo hdparm -i /dev/sdb /dev/sdb: SG_IO: bad/missing sense data, sb[]: 70 00 05 00 00 00 00 10 00 00 00 00 20 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 HDIO_GET_IDENTITY failed: Invalid argument Gparted correctly identifies the drive as SAMSUNG MP0402H. Any ideas how to remedy the HDIO & SG_IO messages?

Desktop reboots itself on sleep or hibernate

I have been using an ASUS M2NPV-VM motherboard for main home desktop workstation, operating Windows Vista x64. This computer has right from day one not been able to enter hibernate or standby; after Windows performs its final actions and brings the machine down, it would automatically revive itself for a reboot. Updating to the second latest BIOS (1201)has not helped (the latest BIOS revision would induce video refresh problems rendering it unusable). I have been reading related discussions on incidents similar to mine to no avail of a true workable solution. They appear to be more speculative guesses rather than actual knowledge on the inner workings of motherboard hardware. Does anybody have any electronic engineering experience on PC energy-saving standards to provide a more informed opinion how to go about getting this to work? More stories: this motherboard could not even reboot properly the first thing i used it. It was due to refresh rate of the onboard GPU, which had no influe...