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Santiago Rivera
Santiago Rivera

Java Rsa Key Generation Example __LINK__

When you connect to a server over HTTPS the security layer (SSL) uses this mechanism to secure your connection. It however does not use RSA to encrypt your data directly; RSA is a rather slow algorithm. Instead RSA is used to exchange a symmetric key (for example AES) which is then used to encrypt data.

Java Rsa Key Generation Example

In the example we get an instance of the RSA cipher and set it up in encrypt mode where we also pass in the public key used to encrypt the message. We pass in the bytes of the plainText string in one go and end up with a byte array of encrypted bytes. These bytes then get base 64 encoded and returned.

It looks quite similar to our encrypt/decrypt functions. We get a Signature of type SHA256withRSA, initialize it with the private key, updated it with all the bytes in our message (you can do this in chunks with for example large files) and then generate a signature with the .sign() method. This signature is then returned as a Base64 encoded string.

The example shown here can be used to generate base64 encoded public keys and the same keys can be shared with javascript or Android client to encrypt all the request that has to travel through the wires to reach to the server and the server can decrypt that using the private key.

Now We have that has methods defined for RSA encryption and decryption.Let us discuss about encryption first. As we discussed above the public key generated is in X.509 format and we use public key for encryption.Hence, we need X509EncodedKeySpec class to convert it again to RSA public key.Remember, that we have base64 encoded public keys.Hence, first let us first Base64 decode and generate the public key.

With every doubling of the RSA key length, decryption is 6-7 times times slower.Hence, when there are large messages for RSA encryption, the performance degrades.In such scenarios, we first do an AES encryption of the messages and the key used for AES encryption is RSA encrypted and sent to the server. This technique can be used by the Javascript or Android client for sending sensitive payloads to the server.We have demonstrates this in another article of RSA encryption in javacript and decryption in Java.

Note that this code is just a toy example of RSA, and should never be used for any vaguely serious security product. Unlike hashes and symmetric key cryptography, RSA has many subtle gotchas that require a lot of research and careful implementation. To barely scratch the surface, some pitfalls include ensuring that the prime factors p and q are not weak, the message is properly padded, multiplication/modulo/exponentiation are computed without branches or data-dependent timing, etc.

Also, note that there are good quality domain parameters available for both DSA and Diffie-Hellman and thus there is no need to generate your own. A common performance issue with DSA and Diffie-Hellman keys are due to users generating their own parameters when there is no need to; parameter generation for both these algorithms is quite expensive.

The following will only provide examples of the request messages since what comes back from a server once a request has been sent in, is up to the server. Often it is a CMS SignedData message containing one or more certificates,. Although in the case of CRMF, it can also be a CMS EnvelopedData message containing an encrypted CMS SigneData message containing one or more certificates. This guide covers the clients, for more information about the server-side, see How to Generate Certificates and CRLs.

Optional data is added to PKCS10 certification requests by including attributes in the request body. The following example code shows how to add an email address to the certification request by adding a request to include the SubjectAlternativeName extension in the certificate the CA will issue.

In some ways, in terms of functional content, the only real difference between the above example is the presence of the certificate request ID, which is simply an integer value specified by the certificate requester and echoed back in the certificate response to allow for certificate requestors that may request multiple certificates. Other than that, you can use the same algorithms suggested before with the key types required.

Note that the code example uses a different sender to the subject used in the CRMF request that you want to create the certificate for. As you are expecting the CA to issue the certificate based on your word, the request is validated using a shared secret, which can be used to calculate a MAC. This makes sense where a client application might be issuing certificates for multiple entities. Where the client application is not also generating the private keys, one of the other POP modes that confirm possession of the private key by the entity ultimately using the certificate should be used.

Note: The authors of the original RSA paper carry out the key generation by choosing d and then computing e as the modular multiplicative inverse of d modulo φ(n), whereas most current implementations of RSA, such as those following PKCS#1, do the reverse (choose e and compute d). Since the chosen key can be small, whereas the computed key normally is not, the RSA paper's algorithm optimizes decryption compared to encryption, while the modern algorithm optimizes encryption instead.[1][21]

Both of these calculations can be computed efficiently using the square-and-multiply algorithm for modular exponentiation. In real-life situations the primes selected would be much larger; in our example it would be trivial to factor n = 3233 (obtained from the freely available public key) back to the primes p and q. e, also from the public key, is then inverted to get d, thus acquiring the private key.

Heninger says in her blog that the bad keys occurred almost entirely in embedded applications, including "firewalls, routers, VPN devices, remote server administration devices, printers, projectors, and VOIP phones" from more than 30 manufacturers. Heninger explains that the one-shared-prime problem uncovered by the two groups results from situations where the pseudorandom number generator is poorly seeded initially, and then is reseeded between the generation of the first and second primes. Using seeds of sufficiently high entropy obtained from key stroke timings or electronic diode noise or atmospheric noise from a radio receiver tuned between stations should solve the problem.[40]

Strong random number generation is important throughout every phase of public-key cryptography. For instance, if a weak generator is used for the symmetric keys that are being distributed by RSA, then an eavesdropper could bypass RSA and guess the symmetric keys directly.

The Java Cryptography Architecture (JCA) allows developers to easily integrate security into their application code. JCA provides a set of APIs for digital signatures, message digests, certificate validation, encryption (symmetric/asymmetric ciphers), key generation and so on. In this article I show how to implement the data encryption and decryption with public-key cryptography (also known as asymmetric cryptography). To do this, I will generate a 2048 bit sized RSA public/private key pair. The public key is used to encrypt a plaintext file, whereas the private key is used to decrypt the ciphertext.

The AsymmetricCipher class has a method to generate a key pair with the object. The encrypt and decrypt methods use the javax.crypto.Cipher to encrypt/decrypt the data bytes .

The first problem we met here is that Java RSA key reading functions do not understand the PKCS1 PEM format. Thanks to this solution and this example, we have the following working code which may read the same keys I used in Node:

The reason is that default Java RSA algorithm has different settings (padding etc.) than Node.js. Some articles explaining it: -castle-vs-java-default-rsa-with-oaep , -down-rsa-ecb-oaepwithsha-256andmgf1padding.

If you need to set parameter values that use spaces, ampersands (&), equals signs (=), or other special characters, youshould URL-encode the special characters. For example, if you need tospecify a value that contains a space, ampersand, and equals sign in the query_tag session parameter:

Note that this example uses an account in the AWS US West (Oregon) region. If the account is in a different region or if theaccount uses a different cloud provider, you need tospecify additional segments after the account locator.

As an alternative, you can set the nonProxyHosts parameter in the connection string or Properties object tobypass the proxy for specific communications. For example, Amazon S3 access can be bypassed by specifyingnonProxyHosts="".

If you do not explicitly specify a logger for the driver using either of the JVM options described above and you do not have a custom logger defined on the classpath (or you are using a driverversion earlier than 3.0.4), the driver uses java.util.logging by default. However, the following default behavior applies:

For simplicity the Private Key is hard coded in above example. However, in real production system it will be loaded from environment variable, or a secret vault (Hashicorp Vault or AWS Parameter Store).

The two transfer protocols that are used to access a Git server are HTTPS and SSH (short for Secure Shell). (The git and local protocols are unusable for any but the most basic development environments.) HTTPS uses a username and password for authentication. SSH uses public-key cryptography for authentication and data encryption. SSH is commonly used when a system or process (for example, a build server) requires access to a Git repository.

Public-key cryptography uses a public and private key. The public key is stored on the server and the private key is stored with the client. In this example, we will show how to generate a public and private key pair to use for SSH authentication with a Git server.


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