Session Key Generation In Java
- Session Key Generation In Java Download
- Session Key Generation In Java Download
- Session Key Generation In Java Free
Apr 13, 2017 Prepackaged keys. Both the MITREid Connect server webapp and the Simple Web App client come pre-packaged with public/private RSA key pairs, found in the keystore.jwks file included in each project's src/main/resources/ directory.
What is a session key? A session key is a single-use symmetric key used for encrypting all messages in one communication session. Scenario: Alice would like to establish a secure communication with Bob. But she cannot provide the key in plain text, otherwise someone sniffing the communication might be able to decrypt the information later on. Jul 19, 2002 The Java platform, both its base language features and library extensions, provides an excellent base for writing secure applications. In this tutorial, the first of two parts on Java security, Brad Rubin guides you through the basics of cryptography and how it is implemented in the Java programming language, using plenty of code examples to illustrate the concepts. Choosing a session ID algorithm for a client-server relationship. Ask Question. I would point out that PHPs built in session generator isn't all that great. You need to actually perform a key exchange and encrypt the session key in transit to prevent it being able to be captured. The only exception to this would be if the client has a. Key generators are constructed using one of the getInstance class methods of this class. KeyGenerator objects are reusable, i.e., after a key has been generated, the same KeyGenerator object can be re-used to generate further keys. There are two ways to generate a key: in an algorithm-independent manner, and in an algorithm-specific manner. Session Management in Java Servlet Web Applications is a very interesting topic. Session in Java Servlet are managed through different ways, such as Cookies, HttpSession API, URL rewriting etc. This is the third article in the series of Web Applications tutorial in Java, you might want to check out earlier two articles too. Java Web Application Tutorial. How to Use Sessions. To use a session, first create a session using the HttpServletRequest method getSession. Once the session is established, examine and set its properties using the provided methods. If desired, set the session to time out after being inactive for a defined time period, or invalidate it manually.
If you like this post, you might like my book: API Security in Action (use discount code fccmadden to get 37% off when ordering).
Update 2 (17th May, 2017): I’ve written some notes on correctly validating ECDH public keys.
Update (20th April, 2017): I’ve noticed that this article gets by far the most daily hits on my blog. This worries me that people are using this code as a template for building real ECDHE key agreement, when it was only intended as a guide to the Java API. There are a lot of details in safe construction of such a protocol. More secure alternatives than to trying to roll this yourself include the various complete protocols listed at the end of the article. With that said, we’ll get back to the original article:
Diffie-Hellman key agreement (DH) is a way for two parties to agree on a symmetric secret key without explicitly communicating that secret key. As such, it provides a way for the parties to negotiate a shared AES cipher key or HMAC shared secret over a potentially insecure channel. It does not by itself provide authentication, however, so it is vulnerable to man-in-the-middle attacks without additional measures. There are several ways to provide these additional measures (e.g. signing the ephemeral public keys using a CA-issued certificate, or using a protocol like OTR), but we will not discuss them here, or go into the details of how the key agreement works. Java provides support out-of-the-box for both original discrete log DH and elliptic curve (ECDH) key agreement protocols, although the latter may not be supported on all JREs. ECDH should be preferred for any new applications as it provides significantly improved security for reasonable key sizes.
As is often the case in Java, the use of these classes can be a bit convoluted. Here we demonstrate simple Java code for ECDH key agreement on the command line. We only demonstrate ephemeral key agreement, in which the two parties generate unique public/private key pairs at the start of the protocol and throw them away once the shared secret has been negotiated. This can form the basis for perfect forward secrecy.
WARNING: the code here is not a complete security protocol and should be used for reference on the Java API only.
The Code
The complete code example is as follows:
To use the example, compile it and then run two instances of it (possibly on different computers). It will print out a hex-encoded ephemeral public key value and then wait for the public key from the other instance. Simply copy+paste this values from one to the other (and vice-versa) and then it will print out the computed shared secret, again hex-encoded and finally a secret key derived from the shared secret.
Let’s walk through the example step-by-step. Firstly, we import a vast number of different classes. We’ll discuss what all of these are for when we get to them.
Step 1: Generate ephemeral ECDH key pair
The first step is to generate an ephemeral elliptic curve key pair for use in the algorithm. We do this using the aptly-named KeyPairGenerator using the “EC” algorithm name to select Elliptic Curve key generation:
By setting the key size to 256-bits, Java will select the NIST P-256 curve parameters (secp256r1). For other key sizes, it will choose other NIST standard curves, e.g. P-384, P-521. If you wish to use different parameters, then you must specify them explicitly using the ECGenParameterSpec argument.
Step 2: Exchange the public keys
The next step is to send our public key to the other party and to receive their public key. In this case, we achieve this by simply printing them out and requiring a human being to perform the communication. No authentication is performed. This means that we cannot be sure that the public key we received is really from the other party and not from a man-in-the-middle.
We assume that the other party is also using a NIST P-256 curve public key. We also assume that the output of PublicKey.getEncoded() is an X.509-encoded key. This turns out to be true in the Oracle JRE, but I cannot find any documented guarantee of this behaviour. A more robust approach would be to communicate the ECPoint and ECParameterSpec of the public key, and use an ECPublicKeySpec to reconstruct the key, but that is even more work.
Step 3: Perform key agreement
The actual ECDH key agreement is straightforward once we have exchanged public keys.
We grab an instance of the ECDH key agreement protocol. The first step is to initialise it with our private key. Then we pass it the other party’s public key via the doPhase() method. We pass true as the second argument to indicate that this is the last phase of the agreement (it is the only phase in ECDH). Diffie-Hellman works by calculating a shared secret based on our private key and the other party’s public key, so this is all we need in this case. The magic of DH is that each party will calculate the same value despite having different sets of keys available to them. Nobody listening in on the exchange can calculate the shared secret unless they have access to one of the private keys (which are never communicated).
Session Key Generation In Java Download
Step 4: Extract the shared secret and derive keys
The final step is to extract the shared secret and then derive a key from it.
Note that it is not advisable to use the shared secret directly as a symmetric key for various reasons. In particular, while the derived secret is indistinguishable from a randomly selected element from the set of all possible outputs of the elliptic curve group, this is not the same thing as a uniformly random string of bits. Viewed as a string of bits, it will have some structure to it. Put another way, the P-256 curve provides roughly equivalent security to a 128-bit secret key, yet the output shared secret is 256 bits. This reveals that the shared secret does not really provide 256 bits of “random” key data. There are further reasons for not using the shared secret directly, depending on the usage. For instance, the security considerations section of RFC 7748 advises to derive a key from the shared secret plus both public keys if we intend to use the key for authentication (this RFC uses different curves than we use here, but it is good advice regardless):
Designers using these curves should be aware that for each public
key, there are several publicly computable public keys that are
equivalent to it, i.e., they produce the same shared secrets. Thus
using a public key as an identifier and knowledge of a shared secret
as proof of ownership (without including the public keys in the key
derivation) might lead to subtle vulnerabilities.
We adopt the approach described in the libsodium documentation, of deriving a key by hashing the shared secret and both public keys, but using SHA-256 rather than BLAKE2. These choices of algorithms and curves are purely for convenience because they are readily available on the JVM without 3rd party libraries (e.g. Bouncy Castle). The only trickiness is to ensure that we feed the public keys into the hash in the same order on both sides of the agreement protocol. For simplicity, we do this by just sorting them lexicographically.
Et voila! Both parties now have the same derived key, which can be used for an AES cipher or HMAC key or however you wish. A more sophisticated key derivation function, such as HKDF, can be used to derive further keys (for instance, separate keys sending data in each direction, which is recommended).
There are a number of complete protocols that build upon this basic agreement mechanism, adding authentication and other details:
- TLS includes this as the various ECDHE_ cipher suites, such as ECDHE_ECDSA_WITH_AES256_GCM_SHA384 (in TLS 1.2 or earlier, TLS 1.3 cipher suites only specify the symmetric encryption component, with key agreement and authentication being negotiated via extensions instead), which means ephemeral ECDH where the exchanged ephemeral public keys are signed using long-term ECDSA keys to provide authentication, and then using the derived secret as a 256-bit key for AES-GCM authenticated encryption. TLS 1.3 mandates cipher suites that support forward-secrecy, including ECDHE. It also has some optimisations to reduce the overhead of the TLS ECDHE handshake, including support for “0-RTT” (zero round-trip time) that allows a client that has previously talked to a server to start a new session and send encrypted traffic on the very first message.
- Protocols like Noise or CurveCP (or CurveZMQ).
- The JSON Web Token (JWT) specs describe a ECDH-ES (ephemeral-static) key agreement and key derivation approach. In this case the recipient has a long-term (static) public key and the sender uses an ephemeral key-pair. This allows the recipient to immediately send a message, without an interactive handshake (i.e., the recipient can be offline, as in email), and it also authenticates the recipient if the long-term public key can be trusted (e.g. via a CA signature, web of trust, etc). However, it gives up forward secrecy, as any compromise of the recipient’s long-term private key will allow decryption of all previous messages sent to that recipient under that key pair. It should be possible to build something like TLS’s 0-RTT mechanism on top of this, but I don’t know of a fully worked out design (and I wouldn’t attempt it unless you know what you are doing).
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Java provides two classes for having random numbers generation - SecureRandom.java and Random.java.The random numbers can be used generally for encryption key or session key or simply password on web server.SecureRandom is under java.security package while Random.java comes under java.util package.The basic and important difference between both is SecureRandom generate more non predictable random numbers as it implements Cryptographically Secure Pseudo-Random Number Generator (CSPRNG) as compare to Random class which uses Linear Congruential Generator (LCG).
Session Key Generation In Java Download
A important point to mention here is SecureRandom is subclass of Random class and inherits its all method such as nextBoolean(),nextDouble(),nextFloat(),nextGaussian(),nextInt() and nextLong().
Session Key Generation In Java Free
Other differences between Random and SecureRandom includes −
Random class uses system time for its generation algorithm as input while SecureRandom class uses random data from operating system such as timing of I/O events.
Due to complex algorithm used in case of SecureRandom which make it more unpredictable,it takes more memory consumption in create secure random numbers than random numbers.
Random class has only 48 bits where as SecureRandom can have upto 128 bits which makes the probability of repeating in SecureRandom are smaller.Due to this also the number of attempts to break Random number prediction comes to 2^48 while that of SecureRandom number is 2^128 which again makes it more secure.