I am new to the security stuff. Is there any way to encrypt and decrypt a security key with the same encryption key?
The real use case is:
Got a security key (32-char), need to hard-coded it into C++ code. But I don't want to have it plain text in C++.
So I choose a password (like 8-char long), pass this to a hash function, like SHA2 and get a 128 bytes hash.
Encrypt the 128 bytes hash with my security key, and save that output encrypted string to C++ code.
When use using the application:
Prompt for password (8-char).
My application take the password and generate the hash through SHA2
Decrypt the encrypted string with the SHA2 hash to get the original security key (32-char).
Since the design has to put the security code in C++, we wanted to find out a way to secure it. With the above mechanism, we are putting the original code in C++ directly.
Related
It is new for me to work with the Crypto++ library and I'm not going to understand why they say CBC-Mode is usually not enough to protect/secure my data.
So can I deal with the CBC-Mode if I would like to use it with user passwords or not?
EDIT (from the comments):
I would like to create a program that encrypt strings with the Crypto++ library. I would like to transform data in order to keep it secret, like user passwords from a program/website, I mean like a password saver/container, with AES.
Can I put text string (serving as password) and binary data (an image file actually) together and encrypt them and then save into new a file. To view the image, first, check if password matches, if yes, read the binary data and save as image. I have to use C++.
Very new to C++. Is that technically possible? Can someone give me some ideas how to start?
If you want it to be actually secure, use somebody else's implementation of an encryption algorithm. What you're looking for is a symmetric key encryption algorithm, such as AES. You'd use the password to encrypt the image, not save the password, and then the password would decrypt said image.
And, as luck would have it, somebody else asked about using AES to encrypt and decrypt things in C and C++ here.
The following project is done in C++ with WinAPI, for encryption/encoding I am using CryptoC++ but I am open to better libraries. I need to encrypt/encode email data, transmit it, then decrypt it at the other end so privileged users can read the email.
My original idea was just to encrypt the email text using SHA256 using my key(eg "MYKEY"). But I think I don't fully understand what hashing is. I understand that a string encrypted with SHA256 or MD5 or AES is impossible to decrypt, BUT I thought that if I encrypt the string with my special key("MYKEY") that I could then decrypt it aslong as I know the special key. Is that correct?
If not can you suggest a library, algorithm or method I can use to achieve my task of encrypting/encoding email text & ONLY being able to decrypt it if I have a key or some shared secret that will allow me to decrypt the data?
As said by Captain Giraffe, a hash algorithm is not an encryption algorithm (though they are both counted in the area of symmetric cryptography). A good hash function has no way to recover a message which fits to the produced hash (other than trying all possible messages to see if they give the same hash). (And also, a hash function has fixed size output, but has a variable size input, which means that there are many messages giving the same hash. It still should be difficult finding even one pair of messages giving the same hash, or a message for a given hash.)
You need an encryption algorithm. Most probably asymmetric encryption (using public keys to encrypt, private keys to decrypt) is a good idea.
Don't invent new cryptographic data formats or protocols. You will make mistakes, which make your product insecure.
For email encryption, use either OpenPGP (RFC 4880) or S/MIME (RFC 3851), or some subsets of one of these.
You can then use any library which supports the necessary algorithms, or some library which supports specifically these file formats.
SHA256 and MD5 are One way functions. i.e. There is no decryption. See Hashing http://en.wikipedia.org/wiki/Cryptographic_hash_function.
But you really need to read up on encryption procedures before attempting to create a secure communication.
That being said wikipedia has an article dedicated to implementations http://en.wikipedia.org/wiki/AES_implementations
Ok, so I need some advice on which encryption method I should use for my current project. All the questions about this subject on here are to do with networking and passing encrypted data from one machine to another.
A brief summary of how the system works is:
I have some data that is held in tables that are in text format. I then use a tool to parse this data and serialize it to a dat file. This works fine but I need to encrypt this data as it will be stored with the application in a public place. The data wont be sent anywhere it is simply read by the application. I just need it to be encrypted so that if it were to fall into the wrong hands, it would not be possible to read the data.
I am using the crypto++ library for my encryption and I have read that it can perform most types of encryption algorithms. I have noticed however that most algorithms use a public and private key to encrypt/decrypt the data. This would mean I would have to store the private key with the data which seems counter intuitive to me. Are there any ways that I can perform the encryption without storing a private key with the data?
I see no reason to use asymmetric crypto in your case. I see two decent solutions depending on the availability of internet access:
Store the key on a server. Only if the user of the program logs in to the server he gets back the key to his local storage.
Use a Key-Derivation-Function such as PBKDF2 to derive the key from a password.
Of course all of this fails if the attacker is patient and installs a keylogger and waits until you access the files the next time. There is no way to secure your data once your machine has been compromised.
Short answer: don't bother.
Long answer: If you store your .DAT file with the application, you'll have to store the key somewhere too. Most probably in the same place (maybe hidden in the code). So if a malicious user wants to break your encryption all he has to do is to look for that key, and that's it. It doesn't really matter which method or algorithm you use. Even if you don't store the decryption key with the application, it will get there eventually, and the malicious user can catch it with the debugger at run time (unless you're using a dedicated secured memory chip and running on a device that has the necessary protections)
That said, many times the mere fact that the data is encrypted is enough protection because the data is just not worth the trouble. If this is your case - then you can just embed the key in the code and use any symmetric algorithm available (AES would be the best pick).
Common way to solve your issue is:
use symetric key algorithm to cipher your data, common algorithm are AES, twofish. most probably, you want to use CBC chaining.
use a digest (sha-256) and sign it with an asymetric algorithm (RSA), using your private key : this way you embed a signature and a public key to check it, making sure that if your scrambling key is compromised, other persons won't be able to forge your personal data. Of course, if you need to update these data, then you can't use this private key mechanism.
In any case, you should check
symetric cipher vs asymetric ones
signature vs ciphering
mode of operation, meaning how you chain one block to the next one for block ciphers, like AES, 3DES (CBC vs ECB)
As previously said, if your data is read andwritten by same application, in any way, it will be very hard to prevent malicious users to steal these data. There are ways to hide keys in the code (you can search for Whitebox cryptography), but it will be definitely fairly complex (and obviously not relying on a simple external crypto library which can be easily templated to steal the key).
If your application can read the data and people have access to that application, someone with enough motivation and time will eventually figure out (by disassembling your application) how to read the data.
In other words, all the information that is needed to decipher the encrypted data is already in the hand of the attacker. You have the consumer=attacker problem in all DRM-related designs and this is why people can easily decrypt DVDs, BluRays, M4As, encrypted eBooks, etc etc etc...
That is called an asymmetric encryption when you use public/private key pairs.
You could use a symmetric encryption algorithm, that way you would only require one key.
That key will still need to be stored somewhere (it could be in the executable). But if the user has access to the .dat, he probably also has access to the exe. Meaning he could still extract that information. But if he has access to the pc (and the needed rights) he could read all the information from memory anyways.
You could ask the user for a passphrase (aka password) and use that to encrypt symmetrically. This way you don't need to store the passphrase anywhere.
I am thinking about making the switch to storing session data in encrypted cookies rather than somewhere on my server. While this will result in more bandwidth used for each request - it will save extra database server load and storage space.
Anyway, I plan on encrypting the cookie contents using RIJNDAEL 256.
function encrypt($text, $key)
{
return mcrypt_encrypt(MCRYPT_RIJNDAEL_256,$key,$text,MCRYPT_MODE_ECB,mcrypt_create_iv(mcrypt_get_iv_size(MCRYPT_RIJNDAEL_256,MCRYPT_MODE_ECB),MCRYPT_RAND));
}
Which in use would produce something like this (base64 encoded for display)
print base64_encode(encrypt('text', 'key'));
7s6RyMaYd4yAibXZJ3C8EuBtB4F0qfJ31xu1tXm8Xvw=
I'm not worried about a single users cookie being compromised as much as I am worried that an attacker would discover the key and be able to construct any session for any user since they know what I use to sign the data.
Is there a way I can verify estimated cracking times in relation to the parameters used? Or is there a standard measure of time in relation to the size of the text or key used?
I heard someone say that the keys needed to exceed 256bits themselves to be safe enough to be used with RIJNDAEL. I'm also wondering if the length of the text encrypted needs to be a certain length so as not to give away the key.
The data will generally be about 200 characters
a:3{s:7:"user_id";i:345;s:5:"token";s:32:"0c4a14547ad221a5d877c2509b887ee6";s:4:"lang";s:2:"en";}
So is this safe?
Yes Rijndael(AES) is safe, however your implementation is far from safe. There are 2 outstanding issues with your implementation. The use of ECB mode and your IV is a static variable that will be used for all messages. An IV must always be a Cryptographic Nonce. Your code is in clear violation of CWE-329.
ECB mode should never be used, CBC mode must be used and this why:
Original:
Encrypted with ECB Mode:
Encrypted using CBC mode:
Avoid using ECB. It can reveal information about what's encrypted. Any two blocks with the same plaintext will have the same ciphertext. CBC would avoid this, but requires an IV to be generated or saved.
Avoid simply saving a key and IV. Generate a 256 bit master key using a cryptographically strong random number generator and save that into you application somewhere safe. Use that to generate session keys for use in encryption. The IV can be derived from the session key. When generating the session key include any and all available data that can be used to narrow the scope of the session key. (e.g. include the scope the cookie, the remote host address, a random nounce stored with the encrypted data, and/or a user ID if it isn't within the encrypted data)
Depending on how the data is to be used you may have to include a MAC. ECB and CBC are not designed to detect any changes to the ciphertext, and such changes will result in garbage in plaintext. You might want to include an HMAC with the encrypted data to allow you to authenticate it before taking it as canon. A session HMAC key must be derived from the session encryption key. Alternatively, you could use PCBC mode. PCBC was made to detect changes in the ciphertext, but its ability to do so is limited by the size of the padding, witch is dependent on the data that is encrypted, and not all crypto APIs will have it as an option.
Once you have gone so far as to include a MAC, then you should consider taking steps against replay attacks. Any time someone can resend old data within the scope of a session is a chance for a replay attack. Making a session key usage as narrow as possible without causing issues for the user is one way to thwart replay attacks. Another thing you could do is include a date and time into the encrypted data to create a window for while the data is to be considered valid.
In summery, protecting the key is just the tip of the iceburg.
If you use a long key, I'd say the key was pretty safe. Some things to concern yourself with:
You are offloading data storage to the client. NEVER TRUST THE CLIENT. This doesn't mean you can't do this, just that you either have to treat the data in the cookie as untrusted (don't make any decisions more serious than what 'theme' to show the user based on it) or provide for a way to validate the data.
Some examples of how to validate the data would be to:
include a salt (so that people with the same session data don't get the same cookie) and
a checksum (so that someone who changes even one bit of the cookie makes it useless).
Rijndael was renamed AES. Yes, it is safe to use.
That said, you should consider carefully what you put in the cookie. It depends on what you have available in the way of storage on your system, but you could simply choose a random number (say a 64-bit number), and store that in the cookie. In your server-side system, you'd keep a record of who that number was associated with, and the other details. This avoids encryption altogether. You use the other details to validate (to the extent anything can be validated) whether the cookie was sent back from the browser you originally sent it to.
Alternatively, you can use a different encryption key for each session, keeping a track of which key was used with which session.
Even if you go with straight encryption with a fixed key, consider including a random number in with the data to be encrypted - this makes it harder to crack using a known plaintext attack because, by definition, the random number can't be known.
AES-128 should be more than sufficient, with no needs to use longer keys - if the key is chosen randomly.
However there are other issues. The first is that you should not use ECB. With ECB a given 128-bit block of plaintext always maps into the same 128-bit ciphertext if the key is the same. This means that adversaries can surgically modify the ciphertext injecting different blocks for which they know the corresponding ciphertext. For example they could mix the data of two different users. With other modes, CBC for example is fine, the ciphertext also depends on the IV (initialization vector), which should be different at every execution of the algorithm. This way, the same plaintext is ciphered differently each time and the adversary cannot gain any advantage. You also need to save the IV somewhere with the ciphertext, no need to protect it. Whenever the chance of reusing the same IV becomes non-negligible you should also change the key.
The second issue is that you should also append a message authentication code. Otherwise you would not be able to distinguish the forged cookies from the good ones.