Generate a private-public key pair using keytool. Protect your existing private rsa key with a passphrase. Save/Load Private and Public Key to/from a file / Published in: Java. Save to your folder(s) Save/Load. Store/Retrieve Private Key/Public Key to/from disk/file:D. Expand Embed Plain Text. JAVA generate RSA Public and Private Key Pairs using bouncy castle Crypto APIs The following sample code generates RSA public and private keys and save them in separate files. You can pass the file names as input parameters and the program generates keys with 1024-bit size.
“The secret of education lies in respecting the pupil.”
― Ralph Waldo Emerson
― Ralph Waldo Emerson
- Generate a new secret key. To generate the key, follow the same process as the one for generating a new private key. You use the Security library in each case. Import encrypted keys more securely. Android 9 (API level 28) and higher allow you to import encrypted keys securely into the Keystore using an ASN.1‑encoded key format.
- The Java KeyGenerator class (javax.crypto.KeyGenerator) is used to generate symmetric encryption keys.A symmetric encryption key is a key that is used for both encryption and decryption of data, by a symmetric encryption algorithm. In this Java KeyGenerator tutorial I will show you how to generate symmetric encryption keys.
- It's impossible to secure a key in an untrusted environment. You can obfuscate your code, you can create a key from arbitrary variables, whatever. Ultimately, assuming that you use the standard javax.crypto library, you have to call Mac.getInstance, and sometime later you'll call init on that instance. Someone who wants your key will get it.
- Oct 21, 2016 Create and read PKCS #8 format private key in java program. In this short article I will show you how to store private key in pkcs8 format in java and again read back the stored key in java. PKCS #8 defines a standard syntax for storing private key information.
Contents
- Conclusion
1. Introduction
In the previous part of this article, we covered the use of RSA for file encryption and decryption in java. Using RSA directly for file encryption will not work since it can only be used with small buffer sizes. In our particular case, with an RSA key size of 2048 bits, we ran into a limitation of a maximum of 245 bytes for the data size.
The solution for this limitation is to use a symmetric algorithm such as AES for encryption while using RSA for encrypting the AES secret key itself. When using AES for encryption, the initialization vector (IV) also needs to be communicated to the receiver for being able to decrypt the message. The entire process of using AES for encryption is covered in detail in this article here.
In the current case, we will generate an AES key, use the AES key for encrypting the file, and use RSA for encrypting the AES key. The output file is generated by including the encrypted AES key at the beginning of the file, followed by the initialization vector (IV) and finally the file data encrypted by AES. This way, just the output file can be delivered to the receiver, instead of the three separate components.
[Note: Check out how to use AES for file encryption and decryption in python.]
2. Java Imports
These are the required java imports for the implementation
3. Generating the AES Key
First step is to generate the AES key which will be used for the encryption. We generate a key of size 128 bits.
We also need the initialization vector of the same size as the key, which we generate as follows (along with the required IvParameterSpec):
4. Loading the RSA Private Key
Load the RSA private key from file using the appropriate class.
5. Save the AES Key
As mentioned above, the first part of the output file contains the encrypted AES key. For encryption, we use the Cipher class with the RSA private key and save it as follows:
6. Write the Initialization Vector
The initialization vector is next written to the output file. This is required for decryption using the AES key.
7. Encrypting the File Contents using the AES Key
Java Get Key
The final step is to encrypt the contents of the file using the AES and write it to the output file.
Close the output file and send it to the receiver.
8. Decrypting the File using the RSA Public Key
Since the private key has been used for encryption, the public key can be used for decrypting the file contents. Remember that the file includes the AES key encrypted with the RSA private key at the beginning followed by the initialization vector, and the encrypted file data itself. So the decryption process has to handle all these steps in order to get at the file data.
9. Load the RSA Public Key from File
Java Generate And Saving Keys Free
We use the following code to load the RSA public key from a file where it has been saved in binary format.
10. Load the AES Secret Key
Open the encrypted file and load the AES secret key. The AES secret key can be obtained from this data by decrypting using the RSA public key.
11. Read the Initialization Vector
Next in the file is the initialization vector. Load it as follows:
12. Decrypt the File Contents
Now comes the actual decryption of the file contents using the AES secret key. The output is written into a file with the extension .ver for verification purposes.
The static method processFile() is defined as before.
At this point the whole file has been decrypted and saved. You can verify that it matches the original file contents.
Conclusion
File encryption and decryption using RSA is somewhat involved since RSA encryption has a very low limit on the data that can be encrypted. The previous part of the article covered the details. To encrypt larger quantities of data, we need to use a symmetric algorithm such as AES for encryption and RSA for encrypting the AES key itself.
Java Generate And Saving Keys 2017
And here is the source code relevant to this blog post.