My Java implementation of RSA encryption.
AES and RSA using javax.crypto. A class to encrypt and decrypt RSA plaintext and ciphertext, as well as to generate RSA key pairs. I'm going to want to be. To use the code, you need corresponding public and private RSA keys. RSA keys can be generated using the open source tool OpenSSL. However, you have to be careful to generate them in the format required by the Java encryption libraries. To generate a private key of length 2048 bits: openssl genrsa -out private.pem 2048. Aug 26, 2012 Following example shows how to encrypt/decrypt information using RSA algorithm in Java. The KeyPairGenerator class instance is used to generate the pair of public and private key for RSA algorithm and are saved into the files. The Cipher class instance is used encrypt/decrypt information using the pair of keys generated above. AES and RSA using javax.crypto. Ask Question. /. Created by Gabriel Wittes on 3/15/2016. A class to encrypt and decrypt RSA plaintext and ciphertext, as well as to generate RSA key pairs./ public class RSA /. Returns a new RSA key pair. I'm going to want to be able to generate keys without a constructed instance of the class.
This program aims to provide the means to encrypt and decrypt filesusing the RSA algorithm.
RSAKeyGenerator.makeKey() method, passing in a constant to specify which kind of key should be returned.RSAKey.PUBLIC_KEY for encryptingRSAKey.PRIVATE_KEY for decryptingRSAKey.COMPLETE_KEY for efficient decryption using the Chinese Remainder TheorumRSAKey returned to the appropriate type of RSAKey.RSAPublicKeyRSAPrivateKeyRSACompleteKeyuse() method, passing in the source and destination file paths.sourcedestinationAdditionally, RSATest now contains a main method for testing. Useage is as follows:
java com.rhg.rsa.RSATest plaintext destination
where plaintext is the path to a readable file, and destination is the prefix to use for storage of files created during the tests.
RSATestContents
Let us learn the basics of generating and using RSA keys in Java.
Java provides classes for the generation of RSA public and private key pairs with the package java.security. You can use RSA keys pairs in public key cryptography.
Public key cryptography uses a pair of keys for encryption. Distribute the public key to whoever needs it but safely secure the private key.
Public key cryptography can be used in two modes:
Encryption: Only the private key can decrypt the data encrypted with the public key.
Authentication: Data encrypted with the private key can only be decrypted with the public key thus proving who the data came from.
First step in creating an RSA Key Pair is to create a KeyPairGeneratorfrom a factory method by specifying the algorithm (“RSA” in this instance):
Initialize the KeyPairGenerator with the key size. Use a key size of 1024 or 2048. Currently recommended key size for SSL certificates used in e-commerce is 2048 so that is what we use here.
Ps4 save editor key generator. From the KeyPair object, get the public key using getPublic() and the private key using getPrivate().
Save the keys to hard disk once they are obtained. This allows re-using the keys for encryption, decryption and authentication.
What is the format of the saved files? The key information is encoded in different formats for different types of keys. Here is how you can find what format the key was saved in. On my machine, the private key was saved in PKCS#8 format and the public key in X.509 format. We need this information below to load the keys.
After saving the private key to a file (or a database), you might need to load it at a later time. You can do that using the following code. Note that you need to know what format the data was saved in: PKCS#8 in our case.
Load the public key from a file as follows. The public key has been saved in X.509 format so we use the X509EncodedKeySpec class to convert it.
Save the keys in text format by encoding the data in Base64. Java 8 provides a Base64 class which can be used for the purpose. Save the private key with a comment as follows:
And the public key too (with a comment):
As mentioned above, one of the purposes of public key cryptography is digital signature i.e. you generate a digital signature from a file contents, sign it with your private key and send the signature along with the file. The recipient can then use your public key to verify that the signature matches the file contents.
Here is how you can do it. Use the signature algorithm “SHA256withRSA” which is guaranteed to be supported on all JVMs. Use the private key (either generated or load from file as shown above) to initialize the Signatureobject for signing. It is then updated with contents from the data file and the signature is generated and written to the output file. This output file contains the digital signature and must be sent to the recipient for verification.
The recipient uses the digital signature sent with a data file to verify that the data file has not been tampered with. It requires access to the sender’s public key and can be loaded from a file if necessary as presented above.
The code below updates the Signature object with data from the data file. It then loads the signature from file and uses Signature.verify() to check if the signature is valid.
And that in a nutshell is how you can use RSA public and private keys for digital signature and verification.
Go here for the source code.