I'm creating a web service that stores a list of users with their public keys online, as well as encrypted messages. My end goal was end-to-end encryption.
I initially thought this would be pretty easy -- "Oh, OpenSSL and RSA private/public key asymmetric encryption is great." False. RSA will only encrypt a tiny bit of data, presumably to pass a regular, symmetric key back and forth.
Okay, so I tried to find solutions online. Most of them either ended without a functioning example or pointed at using the command line, all of which seemed excessive and incomplete.
Is there a way to use end-to-end encryption on data with asymmetric keys, or is it all a personal pipe dream? OpenSSL in PHP has a way to do this already, and it's kludgy but it works.
Is there some method I'm missing here?
The common way to encrypt larger amount of data with a asymmetric keys (eg. RSA) is by use of hybrid encryption. In hybrid encryption you mix symmetric and asymmetric encryption. First you generated a random symmetric key, that is used to encrypt the data. Then you encrypt the symmetric key with the asymmetric key. The encrypted data + the encrypted random key are then put together and makes up the full encrypted data.
The openssl_seal() in PHP you refer to, uses hybrid encryption where the symmetric algorithm is RC4. How data is encoded and put together in the encrypted files have been defined by the openssl implementation, and might not necessarily be the way you would want to do it. PGP, as an other example of hybrid encryption, uses it's own way of packing the data.
In any case, hybrid encryption is not something you get out of the box in java, and you typically need to implement each of the encryption + packaging steps yourself, or use one of the libraries that implements there version of this. An example of doing it yourself is this Java code I found that can decrypt messages encrypted with the above mentioned openssl_seal().
An example of using a library for hybrid encryption, could be using the PGP support in Bouncy Castle.
Ebbe's answer is very good, however this question was highly ranked in Google in my attempt to try and find a decent hybrid encryption library (Bouncy Castle's documentation is non-existent and not straight-forward, and GnuPG for Java relies on the OS and is not fully tested). So I thought I'd add on to Ebbe's answer for the weary traveller.
If you can use them, JWTs (JavaScript Web Tokens) could be handy for this. It's also an IETF Standard. There are two different types:
JWS, which is a signed JWT. Plain-text message, but you can verify its authenticity. Which has its own IETF Standard
JWE, which is an encrypted JWT. Which also has its own IETF Standard
Support for JWEs are unfortunately a bit poor at this point in time. However this should hopefully improve. At this point in time (2017-04-11), the only Java JWT library that supports JWEs is BitBucket's Jose4j.
I'm not really sure what you're trying to en- and decrypt, but GnuPG for Java might be a good choice.
It supports public and private keys and can en- and decrypt bigger files and data.
Related
Recently I have some files which are piped from a remote connection as encrypted files and loaded onto an Android app which are decrypted on runtime. I have found that the exact same decryption code is available here along with the keys. Unfortunately it is in Java and hence one that I am not familiar with, I have no experience with encryption. The link for the module is here
https://github.com/fukata/AES-256-CBC-Example/blob/master/java/src/AESUtil.java
The encrypted example is here
https://zerobin.net/?c5fd41740c9301ef#iNG7oNExRZwK4hBEKP7ZORDBj1fcPZxyjLQZeAihGZ8=
I have been trying to decrypt it by using AES utilities found in VB.NET but unfortunately it doesn't seem to work. So my question is are AES encryption methods different from language to language? IE is something encoded by AES in Java different from one in VB.NET - which would mean i would have to translate the java code directly?
Thanks!
You must use the bit-for-bit identical key and initialization vector as well as the same block chaining mode, but other than that, the language in which an encryption algorithm is written does not matter.
"Is AES Encryption different from language to language?" no.
aes is only an algorithm (computation instruction). aes has maybe a reference-implementation, but it has no "one only correct standardized implementation".
the implementation of aes may be a little bit different in any language. for example in vb.net you would typically use "Byte" as type for an unsigned number in an aes-implementation. however java has no unsigned datatypes, so you have to convert the bytes which are representing negative numbers to avoid encoding-problems. but you do not change the real encryption-algorithm. so you can encrypt your data with an aes-implementation in an arbitrary language and decrypt it with an aes-implementation which is written in another language. if this does not work one of the implementations is flawed.
I have just watched a crypto 101 talk which said if you are typing the letters "AES" into your code, you're doing it wrong! The solution was to "just use GPG".
If you are storing your data on the cloud, all readers and writers need to know the key. If the key is a public private key, that's just a slow key but not a more secure key than just having a good password?
What standard alternatives are there to GPG that properly encrypt data at rest but use a shared secret instead of public keys?
I use Java, and would like to use a library, but want interchange with other platforms.
The solution is wrong in terms - you don't use "GPG" but OpenPGP.
Indeed for encryption using shared secrets (passphrases and alike) OpenPGP is optimal, as it supports multiple methods at the same time and includes compression.
The alternative would be to use CMS encryption with keypairs derived (in some predetermined way) from the shared secret. However such scheme is not standard.
I can remember also XML encryption that supports encryption with symmetric keys, but it has certain security flaws.
So OpenPGP is probably the best way to go.
Regarding compatibility - OpenPGP-compliant library should create packets that can be later processed by any other OpenPGP-compliant library or application. Unfortunately OpenPGP implementation in popular BouncyCastle library sometimes produces not compliant packets - we came across its issues several times when packets created with BouncyCastle could not be processed by GnuPG or our SecureBlackbox due to issues in the packet created.
I need help using Bouncy Castle RSA Libraries for a school assignment, but it looks very complicated and I'm trying to learn and need some guidance.
For my assignment I need to just generate a public and private key. Then encrypt a block of message and do timing measurements. Then do the same for decryption.
Could someone point me in the right direction?
The Crypto Library is huge and I'm confused on how to go about this.
Thank you very much.
PS: Basically I need to generate the Key Pairs, Execute the encryption and decryption using different key pairs that are randomly generated.
I would appreaciate any guidance, thanks
Normally with Java you would use the Java Cryptography API's, in the java.security.* and javax.crypto.* packages.
BouncyCastle includes a provider (i.e. an implementation) for this API, but for RSA the one delivered with your JRE should be fine, too. (BouncyCastle additionally also has an own API which does things in other ways.)
You would need the KeyPair and KeyPairGenerator classes for the key generation, and the Cipher class for the actual encryption and decryption operation.
For the timing measurement, repeat the encryption/decryption some thousand times to get reliable data.
I have an Android application, which uses javax.crypto to encrypt some text data in files. Encryption implementation is similar to this. The application works fine with the encrypted data it previously created.
Now, I almost ported my Android application to desktop (JFace/SWT). I'm using the same encryption implementation for the ported application, as it does not depend on any Android-specific API. The ported application works fine with encrypted data it created.
The problem is that desktop application cannot decrypt data, which was saved with Android application. The Android application fails to decrypt data, which was saved with desktop application as well. I double checked bytes streams of plain data and password to encrypt on both platforms. They are the same, so there are no problems with text encoding or so. But encryption routine return different encrypted results on different platforms even input data is byte-to-byte identical.
Does Java crypto API guarantees the same operation on different platforms? Should an encryption provider (AES/128bit in my case) work the same way on Android, Linux and Windows? Is there a way to tune javax.crypto to get interoperability on different platforms?
AES-128 should work the same on both systems. In theory.
In practice there are a lot of details that need to be the same on both systems.
are you using the same padding at both sides?
are you using the same mode (CBC, CTR, ECB) at both sides?
do you have exactly the same password at both sides?
do you have the same IV/Nonce at both sides?
do you have the same key derivation method on both sides?
Check any defaults on both systems. If the defaults don't match then you will need to set one side or the other explicitly.
It is a mistake to depend on a cryptographically-random number generator generating the same random numbers on different platforms. Normally, the cryptographic random salt used in a key-derivation algorithm has to be communicated from sender to receiver. It might be communicated as a secret, but it does need to be communicated. The "master password" is the main secret, of course.
One way these salts are often communicated is as a prefix on the ciphertext. That makes the ciphertext longer than the plaintext, but I don't think that matters in your sample technique.
Also, for a full-up encrypted-message exchange, other parameters of the encryption need to be communicated to the decrypter. You can wire those into your implementations, as you've done here, but depending on reproducibility seems too brittle. It is of course something an attacker can replicate, of course, so it is not part of your secret.
You might want to rethink the key-generation algorithm setup to be something more robust.
Afterthought: What is happening in the current approach is a cryptographically-useful RNG is being used in a way where all the randomness has been removed! The recommendation to check out PBKDF2 and key-derivation generally is a good one.
You'd have to show us some code. One frequent beginner mistake is to store the encrypted data in a String rather than the byte[] it came in. String isn't a container for binary data. This technique can fail in many ways including default charade differences.
I am using password based encryption. My initial thought was to use AES to encrypt the file which contains passwords. Turns out password based encryption does not support AES. It uses DES. AFAIK des is not secure. Is PBEWithMD5AndDES secure enough to thrust my data or should i look for another implementation?
It appears from your comments that what you would like to do is to encrypt a file which contains sensitive information, using a password-based encryption scheme, with a password provided by the user at decrypt-time. The sensitive information in this case also happens to be passwords, but that isn't really relevant. (You should probably update the question to make this more clear).
You are doing the right thing, your problem is just that the SunJCE Java cryptography provider doesn't support AES for password-based encryption. You need to use an alternative provider which does: for example, you could use the Bouncy Castle provider with the algorithm "PBEWITHSHA256AND128BITAES-CBC-BC". (Despite the whimsical name, Bouncy Castle is well-respected).
As for "is DES secure enough for my data", well if the data you're protecting would be worth less than roughly $10,000 to an attacker, then back in 2009 it was probably just secure enough. And in 2014, if your data is worth encrypting at all, the answer is no.
If you have Java 6 available, everything you need is available. Check out this question and look at the accepted answer for a code sample. Since you want to encrypt files, the iv that is generated should be prepended to the file you are writing the ciphertext to, so that it is available during the decryption.
You should not be keeping the passwords in any form other than salted hash digests.
You should then use the operating system permission system to make it such that the hashed password file is only readable by the user which validates passwords.