I have a quite a large file (>50gb) that has no file extension and is possibly encrypted. I created this file a while ago, but I accidentally removed the extension but I think it is possibly a compressed file (e.g. .7z, .rar). I know the password if I am able to identify which application can open it.  How is it possible to identify which file type this file belongs to (bearing in mind it might be encrypted - but I know the encrypted password if there is one)?  I tried using a Hex Editor but weird characters are shown most likely because it is encrypted.  Further Information:  Hopefully this should be helpful:   I would have created this file on a Windows operating system The hex editor has text 0x0 to 0x200 followed by a massive whitespace before contents/text resumes at 0x20000.
7633
I sometimes get files from my clients that have the wrong file extension. For example, the name is image.jpg but the file is actually a TIFF image. In many cases I can clarify it by opening the file in a text editor, looking at the first few bytes, then deducing which file type it is.  This works for me with JPEG, TIFF, GIF and PDF files. However there are many more file types out there.  Is it possible to automate identification of the correct file type by analyzing the containing data?
46035
I have .rar file that is password protected, but I accidentally have forgotten the password. The file extremely important to me.  How can I get my file back? In windows, there was many programs that could remove the password of such a file. Is there one for Ubuntu?
37878
I somehow managed to create a file that doesn't seem to have a filename. I found some information regarding how to get more details of the file in the following   However, I tried some of the suggestions listed and can't seem to delete the file. I'm not sure what I did to create it, but it happened while trying to copy an xml file.   Some info on the file is as follows;  &gt; ls -lb total 296 -rw-r--r--   1 voyager  endeavor  137627 Jan 12 12:49 \177  &gt; file * :               XML document  &gt; ls -i  417777      I tried to find using the inum switch and then pipe that to rm as that seemed like the most foolproof way of getting rid of it. However, the example given at the bottom of the thread linked below failed for me. Example was:  &gt; find -inum 41777 -exec ls -al {} \; find: illegal option -- i find: [-H | -L] path-list predicate-list   so I tried using the path list first like the following, but that didn't work either:  &gt; find . -inum 41777 -exec ls -al {} \;   I'm not sure what the non-printable character \177 is or how I can pass that to an rm command, but I really want to make sure I don't mess up any other files/directories in my attempt to delete this file.
110486
So I am using cryptopp to encrypt a file in a project and I am using AES-GCM. I have a 256bit key and a 128bit ivec and a 128bit tag that I use to encrypt files.  However, I want to know where the authentication tag is stored? I notice if I specify a tag size of 0 then the encrypted file size is the same number of bytes as the original file.  Is the authentication tag simply appended to the end of the file?
19576
Let's say that there is a binary file encrypted with AES in CBC mode (i.e. using a key and initialization vector). If key is known, but IV is not, is it easy to fully decrypt the file?  How hard is it?
86143
How can I find all files I can not write to?  Would be good if it takes standard permissions and acls into account.  Is there an "easy" way or do I have to parse the permissions myself?
7502
Possible Duplicate:          I have a folder named "ed6b7b66d9c1d645bfce0f8b33c3" under C: of Windows 7. I was wondering what its purpose is and if it is safe to delete? Thanks!  It takes up 120 MB. Its content is as follows:
67398
Windows 7 Ultimate 64bit:  I'm looking for a way to find all the files in a directory that are NOT of a specific file type or extension.  Example: I'd like to find every file that isn't an .mp3 in my music folder (and all sub folders).
100586
This comes following a discussion with a colleague.   My plaintext file plain consists of a about 100,000 lines of "all work and no play...". It's size is: 2.2 MB. Compressed it is: 5.4kB I encrypt the original:  openssl aes-128-cbc -in plain -out plain.ENC   plain.ENC is marginally bigger than the original, which I would expect. I compress the encrypted copy: gzip plain.ENC. But I observe that the compressed copy is now marginally larger than plain.ENC.   Assuming the entropy of the original file is on the order of ~1000-10000 bits, why is the corresponding ciphertext incompressable? My intuitive notion of the entropy of a string is the minimal number of bits required to produce that string. If the string is the 3 MB long cipher text, it was generated with a 1000-bit entropy string encrypted with an AES implementation (probably no more than a few thousand bits), as well as a few-hundred bit key. Intuitively, to me, the entropy of the cipher text should be no more than the sum of the entropies of the strings and procedures that generate it.  So, my question is: Is my intuitive notion completely wrong? If we extended the low-entropy file to be orders of magnitude larger, would we begin to observe compressibility in the ciphertext?
82331
From , there are $14$ bytes specifying the file format of the key. I am still quite confused about the format bytes. For example, the following public key 30 82 01 0a 02 82 01 01 00 8e a3 d1 c7 9c 86 05 52 3d 70 9a 5b 24 8a 6e ab 8f 5d 8d 9a 44 5f 25 78 c7 ba bd 3a a6 e1 36 b8 55 88 18 d7 ea e8 14 2c 68 8f e7 fe 94 4c f3 fd ad 0b e6 d2 eb 9e d2 66 b4 3a 3b d1 bb 5d d5 2a 53 7e 0f 1d ba ec 03 29 9d 47 50 3b 99 fb 4a 3a 80 a2 23 3e d7 11 e3 de a8 8d ab 7c 90 d0 92 af 36 b8 8b 28 fd 80 ec bc 37 6d 23 44 86 4e 28 19 1d 18 37 af 44 a9 40 b3 f6 e7 6c ad 56 5d 6f ff 3b e3 a5 cc 23 5c 54 2a 47 28 5b 29 f3 45 8e 69 98 ad 57 45 2e 60 bd ac 55 fc 35 e8 47 9f 98 0d f9 ea 9d 55 35 c9 db af 24 d2 bc 18 12 02 53 d6 aa ef 9c c9 11 c9 8e d7 7c 4f 2f 22 0f 66 b1 bf 06 a5 fa 87 22 9f ff f6 20 75 e7 51 87 26 30 c2 e1 a5 30 2c a1 fc 47 a5 f7 a5 38 d3 cc 8d 0e ee 5a 54 ee a2 f9 ff d0 0a 0f 18 7f 94 d2 04 5e 1f 25 ca be 4e 30 c3 40 00 ed a4 ce 58 ab 23 39 2d 02 03 01 00 01 is taken from google's certificate. The first byte $30$ means it is a sequence. Then I don't know what is the meaning from 2nd byte to 9th byte. Can anyone explain to me? UPDATE: The 2nd byte (82) means that the following 2 bytes give the length of the sequence. The 5th byte tells us that it is an integer. The byte following it tells us the length and the value of the integer (I guess). Then the rest I have no idea. Also what do the last 3 bytes stand for? I can't find format start with $01$.
108285
Background info: I am planning on making a filehost with which one can encrypt and upload files. To protect the data against any form of hacking, I'd like not to know the encryption key ($K$) used for a file, so the user will have to asymmetrically encrypt $K$ and send it as well. The reason for this double encryption is that you can still share (individual!) files with other accounts by encrypting $K$ with the public keys of those users, too.  My problem is: How can a user can get a public and private key without the server saving/knowing the private key and without the user having to remember a passphrase of 250 hex characters?  Question: Is there a way to derive a key pair from a password, like PBKDF-2 does for symmetric encryption? Suggestions on rearranging the cryptographic steps in an easier way are welcome, too.  Alternatively: It is also possible to encrypt the private key with a PBKDF-applied password and store it on the server, but I'd like to keep things 'simple'. ;)  Note: At this point I don't care if it requires RSA, ECC or an obscure cryptography scheme.
100581
I've got a  file, and I can't figure out how to open it. How can I open it?
12566
At the moment, if I download a compressed file, it could be any of a .tar.gz archive, a tar.bz2 arhive, a .zip archive or a .gz archive. And each time I do so, I have to remember what the command line options for that program are.  Is there any CLI program where I can just go:  undocompression somefile.??  and let it figure out what format the archive is in? (overly long name used to avoid conflicting with any real program)
16115
So, I was having this weird thought. If the checksums(MD5 or SHA...) are unique to any file and are modified if any part of the file is edited, why cant the checksums be decoded back to get the original file? That is if I want to send a large(say 700MB) video, instead I could send just the hash and the file be decoded locally in my friend's computer. I know the thought is stupid, but is it possible by any chance? Or am I missing some thing here? And forgive me if I'm wrong, I ain't a professional.
41448
I see you have succussfully answered this question previously but it is not specific to my system.  I have downloaded your file and created the relevant dump file but I don't know how to analyse it. Can I upload it to you for some advice please?
17113
A friend sent a long a file (a .rar) he wanted me to check out for him before he installed it.  I downloaded it and unrared it with no problems, but it was full of .exe's instead of the intended contents (fonts) so I advised him to delete it immediately and not use.  I then proceeded to do the same, but the folder simply will not delete. Oddly the files went fine, and I never ran anything, but this is what I'm seeing:   Could not find this item  This is no longer located in C:\Users\This_User\Desktop. verify the item's location and try again.   I've tried the following things with no help:   Using "Unlocker" to Unlock and delete Using move on reboot and rebooting Using PendMoves (from sysinternals) and rebooting Elevating a cmd line, doing a dir /x to get the short name of the folder, and then del 'shortna~1' Moving the folder to a new folder and then trying to delete the parent folder   I'm on Windows 7 RTM, very fresh install. Any thoughts?  Update: Just to confirm, I've run Hijack this and half a dozen other malware detectors, and everything came back clean (no extra processes, no other obvious badness). Rebooting in safe mode didn't help either.
100840
Is it better to encrypt a plain text file before compression, or vice versa?