Ecdsa Key Pair Generation Java
In order to be able to create a digital signature, you need a private key. (Its corresponding public key will be needed in order to verify the authenticity of the signature.)
Oracle Java documentation is a little sparse on the topic, but it does look like with the SunJCE, a key generated asEC can be used with either ECDH or ECDSA. (I'm not an Elliptic curve expert, but) Theoretically, I believe that the domain parameters for ECDH and ECDSA have the same form, that is the equation of the curve and a base point G. May 20, 2016 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. For a non-technical person, how do I generate a ECDSA key pair easily? Ask Question Asked 7 years, 5 months ago. Active 1 year, 2 months ago. Apr 18, 2010 ECDSA KEY PAIR. 843811 Apr 17, 2010 11:34 PM Hi, does this output look ok? A lot of sequences, prefix and in the middle of the sequence repeat every generation. Nov 22, 2019 ECDSA is using deterministic k value generation as per RFC6979. Most of the curve operations are performed on non-affine coordinates (either projective or extended), various windowing techniques are used for different cases.
- Accredited Standards Committee X9, American National Standard X9.62-2005, Public Key Cryptography for the Financial Services Industry, The Elliptic Curve Digital Signature Algorithm (ECDSA), November 16, 2005. Certicom Research, Standards for efficient cryptography, SEC 1: Elliptic Curve Cryptography, Version 2.0, May 21, 2009.
- In practice, a RSA key will work everywhere. ECDSA support is newer, so some old client or server may have trouble with ECDSA keys. A DSA key used to work everywhere, as per the SSH standard (RFC 4251 and subsequent), but this changed recently: OpenSSH 7.0 and higher no longer accept DSA keys by default.
In some cases the key pair (private key and corresponding public key) are already available in files. In that case the program can import and use the private key for signing, as shown in Weaknesses and Alternatives.
In other cases the program needs to generate the key pair. A key pair is generated by using the KeyPairGenerator class.
In this example you will generate a public/private key pair for the Digital Signature Algorithm (DSA). You will generate keys with a 1024-bit length.
Generating a key pair requires several steps:
Create a Key Pair Generator
The first step is to get a key-pair generator object for generating keys for the DSA signature algorithm.
As with all engine classes, the way to get a KeyPairGenerator object for a particular type of algorithm is to call the getInstance static factory method on the KeyPairGenerator class. This method has two forms, both of which hava a String algorithm first argument; one form also has a String provider second argument.
A caller may thus optionally specify the name of a provider, which will guarantee that the implementation of the algorithm requested is from the named provider. The sample code of this lesson always specifies the default SUN provider built into the JDK.
Put the following statement after the
line in the file created in the previous step, Prepare Initial Program Structure:
Initialize the Key Pair Generator
The next step is to initialize the key pair generator. All key pair generators share the concepts of a keysize and a source of randomness. The KeyPairGenerator class has an initialize method that takes these two types of arguments.
The keysize for a DSA key generator is the key length (in bits), which you will set to 1024.
The source of randomness must be an instance of the SecureRandom class that provides a cryptographically strong random number generator (RNG). For more information about SecureRandom, see the SecureRandom API Specification and the Java Cryptography Architecture Reference Guide .
The following example requests an instance of SecureRandom that uses the SHA1PRNG algorithm, as provided by the built-in SUN provider. The example then passes this SecureRandom instance to the key-pair generator initialization method.
Some situations require strong random values, such as when creating high-value and long-lived secrets like RSA public and private keys. To help guide applications in selecting a suitable strong SecureRandom implementation, starting from JDK 8 Java distributions include a list of known strong SecureRandom implementations in the securerandom.strongAlgorithms property of the java.security.Security class. When you are creating such data, you should consider using SecureRandom.getInstanceStrong(), as it obtains an instance of the known strong algorithms.
Generate the Pair of Keys
The final step is to generate the key pair and to store the keys in PrivateKey and PublicKey objects.
- Using the Bouncy Castle Specific APIs
- Key Pair Generation
- Using a KeyFactory
- Using the JDK APIs
- Key Pair Generation
- Using a KeyFactory
Key pair generation in elliptic curve follows the same principles as the other algorithms, the main difference being that, unlike algorithms such as RSA, elliptic curve keys exist only in the context of a particular elliptic curve and require to have curve parameters associated with them to be of any use.
Having said that, there is one anomaly with elliptic curve over other algorithms in that there are two APIs supported by the provider for using them. The reason for this is that JDK elliptic curve support was only introduced with the release of JDK 1.5. Prior to that providers supporting elliptic curve had to include some provider specific classes to allow it to be used, and as Bouncy Castle has supported elliptic curve since release 1.04 it had to provide it's own API.
Other than differences in parameters the generation of elliptic curve keys is identical for both Fp and F2m.
Like other asymmetric algorithms, elliptic curve private keys produce DER encodings of PKCS8 PrivateKeyInfo objects and elliptic curve public keys produce DER encodings of X.509 SubjectPublicKeyInfo objects.
The following example shows a simple case of copying a key pair using the getEncoded() method on the public and private keys and the X509EncodedKeySpec and PKCS8EncodedKeySpec classes.
The Bouncy Castle API for elliptic curve consists of a collection of interfaces and classes defined in org.bouncycastle.jce, org.bouncycastle.jce.interfaces, and org.bouncycastle.jce.spec packages which provide provider specific support for elliptic curve keys, parameters, and named curve handling.
Key Pair Generation
Key pair generation can be done using explicitly created parameters or by retrieving a named curve from a lookup table.
From Explicit Parameters
An org.bouncycastle.jce.ECParameterSpec is required to construct an elliptic curve key. The long way of creating one of these is to create the ECParameterSpec object from a Bouncy Castle ECCurve object and an associated base point and order.
Normally you'd only do this if the curve you want is not already present in one of the named curve tables (see below), but if you had a set of parameters you wanted to use it would look something like this:
As you can see it is a two step process. First you need to create the curve and then you need to associate the curve with a base point and an order using an ECParameterSpec which is then used to initialise the KeyPairGenerator object.
From Named Curves
Named curves are handled in the Bouncy Castle provider by associating a parameter set with a name using an extension of ECParameterSpec, ECNamedCurveParameterSpec, which can be found in org.bouncycastle.jce.spec. Normally you would not create one of these parameter spec objects directly, but you would retrieve it from one of the two lookup tables in org.bouncycastle.jce - ECNamedCurveTable if you are using ECDSA, or ECGOST3410NamedCurveTable if you are using GOST310-2001. Both classes support a getNames() method which will tell you what named curves are currently supported.
Assuming you were wanting to use the X9.62 curve prime192v1, the code would look something like this:
Using a KeyFactory
From Explicit Parameters
The Bouncy Castle provider also supports key spec objects for cases where the key material is already available and the use of a KeyPairGenerator is not required. In this case the regular KeyFactory class is used and the Bouncy Castle specific classes ECPublicKeySpec and ECPrivateKeySpec are used to hold the material for the public and private keys respectively.
As you can see the first step is identical to that used for the KeyGenerator, except this time the ECParameterSpec is used to create an ECPrivateKeySpec containing the private value and the parameters, and an ECPublicKeySpec containing the public point and the curve parameters.
These can then be passed to a KeyFactory as follows:
and the resulting keys can then be used as the ones produced by the KeyPairGenerator were.
With Named Curves
As with the key pair generation example, if you know the curve associated with the keys you have been given is for a named curve, you can replace the construction of the ECParmeterSpec above with a named curve lookup using one of the named curve tables from org.bouncycastle.jce.
If you are using JDK 1.5 or later there is local support in the JDK for generation of elliptic curve keys.
Key Pair Generation
With Explicit Parameters
If you're using explicit parameters to generate keys:
With Named Curves
The JDK also supports the use of Named Curves using the ECGenParameterSpec, which simply passes the name of the curve to the provider for interpretation. For example to use the X9.62 curve prime192v1 with the Bouncy Castle provider to generate an Elliptic Curve key pair the code would look something like the following:
Using a KeyFactory
With Explicit Parameters
/generate-ssh-keys-ubuntu-1804.html. As can be seen in the following code, the explicit parameters case for JDK 1.5 follows the same steps as for the Bouncy Castle provider as can be seen in the following code:
The one difference of note is the use of the ECPointUtil class to handle an encoded point. The is a Bouncy Castle specific class which can be used to convert point encodings into JDK ECPoint objects. In the case where the point would have been added from its base BigInteger objects the following code could replace the call the ECPointUtil:
With Named Curves
Generate Ecdsa Ssh Key
This case isn't actually directly supported in the JDK. Bouncy Castle does provide a helper class org.bouncycastle.jce.spec.ECNamedCurveSpec which can be used to wrap the return value from the named curve tables provided in org.bouncycastle.jce: