This approach is used in many applications and scenarios. There are Web Services or Single Sign-On implementations, which enforce you to use the same key pair for both operations. X.509 certificates do not allow you (by default) to determine, if a given RSA key must be used for encryption/decryption or for signing/verification.

1. Generating an RSA Key Pair Problem You want to use RSA to encrypt data, and you need to generate a public key and its corresponding private key. Solution Use - Selection from Secure Programming Cookbook for C and C Book.
2. Oct 23, 2008 Hi all, The other day a colleague of mine asked me if I had a.NET version of the C sample in How to generate key pairs, encrypt and decrypt data with CryptoAPI post. C sample calls CryptoAPI directly (and you know we can do the same thing in.NET through P/Invoke), but the idea was to use.
3. Oct 05, 2007 To add a comment to the public key file when generating the key add to the key generation command -C 'you comment'. For example to generate 4048 bit RSA key with “home machine” as a comment you will do the following: ssh-keygen -b 4048 -t rsa -C 'home machine'.
4. For what I have learned about generating RSA keys with C#, RSACryptoServiceProvider gives a pair of keys, a public one and a private one. So what I tried to do was create those 2 keys, getting the public key by creating a new RSACryptoServiceProvider and assigning it a public modulus and a public exponent from the first RSACryptoServiceProvider.
5. Jun 22, 2012 SSH keys provide a more secure way of logging into a virtual private server with SSH than using a password alone. With SSH keys, users can log into a server without a password. This tutorial explains how to generate, use, and upload an SSH Key Pair.
6. I wrote the following C code for generating keys for RSA. Keygen is a function to generate private and public keys. Here ekey is Public key and dkey the private key. Both are passed by reference. Then phival is the Euler totient function (ie., phi(x)). (This was calculated sometime earlier, not shown).

Download and install the OpenSSL runtimes. If you are running Windows, grab the Cygwin package.

OpenSSL can generate several kinds of public/private keypairs.RSA is the most common kind of keypair generation.^[1]

Other popular ways of generating RSA public key / private key pairs include PuTTYgen and ssh-keygen.^[2][3]

Generate an RSA keypair with a 2048 bit private key[edit]

Execute command: 'openssl genpkey -algorithm RSA -out private_key.pem -pkeyopt rsa_keygen_bits:2048'^[4] (previously “openssl genrsa -out private_key.pem 2048”)

e.g.

Make sure to prevent other users from reading your key by executing chmod go-r private_key.pem afterward.

Extracting the public key from an RSA keypair[edit]

Execute command: 'openssl rsa -pubout -in private_key.pem -out public_key.pem'

e.g.

A new file is created, public_key.pem, with the public key. None of the key or diamond generators work for choices.

It is relatively easy to do some cryptographic calculations to calculate the public key from the prime1 and prime2 values in the public key file.However, OpenSSL has already pre-calculated the public key and stored it in the private key file.So this command doesn't actually do any cryptographic calculation -- it merely copies the public key bytes out of the file and writes the Base64 PEM encoded version of those bytes into the output public key file.^[5]

Viewing the key elements[edit]

Execute command: 'openssl rsa -text -in private_key.pem'

All parts of private_key.pem are printed to the screen. This includes the modulus (also referred to as public key and n), public exponent (also referred to as e and exponent; default value is 0x010001), private exponent, and primes used to create keys (prime1, also called p, and prime2, also called q), a few other variables used to perform RSA operations faster, and the Base64 PEM encoded version of all that data.^[6](The Base64 PEM encoded version of all that data is identical to the private_key.pem file).

Password-less login[edit]

Often a person will set up an automated backup process that periodically backs up all the content on one 'working' computer onto some other 'backup' computer.

Because that person wants this process to run every night, even if no human is anywhere near either one of these computers, using a 'password-protected' private key won't work -- that person wants the backup to proceed right away, not wait until some human walks by and types in the password to unlock the private key.Many of these people generate 'a private key with no password'.^[7]Some of these people, instead, generate a private key with a password,and then somehow type in that password to 'unlock' the private key every time the server reboots so that automated toolscan make use of the password-protected keys.^[8][3]

Further reading[edit]

C Generate Rsa Key Pair Signature V1

1. ↑Key Generation
2. ↑Michael Stahnke.'Pro OpenSSH'.p. 247.
3. ↑ ^ab'SourceForge.net Documentation: SSH Key Overview'
4. ↑'genpkey(1) - Linux man page'
5. ↑'Public – Private key encryption using OpenSSL'
6. ↑'OpenSSL 1024 bit RSA Private Key Breakdown'
7. ↑'DreamHost: Personal Backup'.
8. ↑Troy Johnson.'Using Rsync and SSH: Keys, Validating, and Automation'.

• Internet_Technologies/SSH describes how to use 'ssh-keygen' and 'ssh-copy-id' on your local machine so you can quickly and securely ssh from your local machine to a remote host.

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How To Generate Rsa Key Pair