I was recently in a meeting where a person needed to generate a private andpublic key for RSA encryption, but they were using a PC (Windows). This is somethingthat is easily done via a terminal using ssh-keygen on Mac and Linux, however on Windows…this tool is not easily accessible to the non-technical person.

• Generate A Public Private Key Pair
• Generate A Public/private Key Pair
• Public Private Key Pair Generator Online

The KeyPairGenerator class is used to generate pairs of public and private keys. Key pair generators are constructed using the getInstance factory methods (static methods that return instances of a given class). A Key pair generator for a particular algorithm creates a public/private key pair that can be used with this algorithm. Generate an ECDSA SSH keypair with a 521 bit private key. Ssh-keygen -t ecdsa -b 521 -C 'ECDSA 521 bit Keys' Generate an ed25519 SSH keypair- this is a new algorithm added in OpenSSH. Ssh-keygen -t ed25519 Extracting the public key from an RSA keypair. Openssl rsa -pubout -in privatekey.pem -out publickey.

It then occurred to me (and a head slapped followed), that I have fairly recentlypublished a library for Javascript RSA encryption which includes private andpublic key generation for RSA encryption. Not only that, but this is allavailable online.

So, if anyone needs an online RSA key generator, look no further than http://travistidwell.com/jsencrypt/demo.

This directly maps to the Open Source GitHub repository found at https://github.com/travist/jsencrypt, soanyone can modify this website to make it better.

And here is an iframe of the RSA key generation tool.

Generate A Public Private Key Pair

The KeyPairGenerator class is used to generate pairs of public and private keys. Key pair generators are constructed using the getInstance factory methods (static methods that return instances of a given class).

Generate A Public/private Key Pair

A Key pair generator for a particular algorithm creates a public/private key pair that can be used with this algorithm. It also associates algorithm-specific parameters with each of the generated keys.

There are two ways to generate a key pair: in an algorithm-independent manner, and in an algorithm-specific manner. The only difference between the two is the initialization of the object:

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• Algorithm-Independent Initialization

  All key pair generators share the concepts of a keysize and a source of randomness. The keysize is interpreted differently for different algorithms (e.g., in the case of the DSA algorithm, the keysize corresponds to the length of the modulus). There is an initialize method in this KeyPairGenerator class that takes these two universally shared types of arguments. There is also one that takes just a keysize argument, and uses the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness is used.)

  Since no other parameters are specified when you call the above algorithm-independent initialize methods, it is up to the provider what to do about the algorithm-specific parameters (if any) to be associated with each of the keys.

  If the algorithm is the DSA algorithm, and the keysize (modulus size) is 512, 768, or 1024, then the Sun provider uses a set of precomputed values for the p, q, and g parameters. If the modulus size is not one of the above values, the Sun provider creates a new set of parameters. Other providers might have precomputed parameter sets for more than just the three modulus sizes mentioned above. Still others might not have a list of precomputed parameters at all and instead always create new parameter sets.

• Algorithm-Specific Initialization

  For situations where a set of algorithm-specific parameters already exists (e.g., so-called community parameters in DSA), there are two initialize methods that have an AlgorithmParameterSpec argument. One also has a SecureRandom argument, while the the other uses the SecureRandom implementation of the highest-priority installed provider as the source of randomness. (If none of the installed providers supply an implementation of SecureRandom, a system-provided source of randomness is used.)

In case the client does not explicitly initialize the KeyPairGenerator (via a call to an initialize method), each provider must supply (and document) a default initialization. For example, the Sun provider uses a default modulus size (keysize) of 1024 bits.

Note that this class is abstract and extends from KeyPairGeneratorSpi for historical reasons. Application developers should only take notice of the methods defined in this KeyPairGenerator class; all the methods in the superclass are intended for cryptographic service providers who wish to supply their own implementations of key pair generators.

Every implementation of the Java platform is required to support the following standard KeyPairGenerator algorithms and keysizes in parentheses:

• DiffieHellman (1024)
• DSA (1024)
• RSA (1024, 2048)

Public Private Key Pair Generator Online

These algorithms are described in the KeyPairGenerator section of the Java Cryptography Architecture Standard Algorithm Name Documentation. Consult the release documentation for your implementation to see if any other algorithms are supported.