Oct 05, 2007 Generating Keys. Generating public keys for authentication is the basic and most often used feature of ssh-keygen. Ssh-keygen can generate both RSA and DSA keys. RSA keys have a minimum key length of 768 bits and the default length is 2048. When generating new RSA keys you should use at least 2048 bits of key length unless you really have a good reason for using a shorter and less secure. The -t option specifies the key generation algorithm (RSA in this case), while the -b option specifies the length of the key in bits. The -f option sets the name of the output file. If not present, ssh-keygen will ask the name of the file, offering to save it to the default file /.ssh/idrsa.
- What Is Rsa Key Generation Windows
- Rsa Key Generation Cisco
- What Is Rsa Key Generation Linux
- Rsa Key Generation Standard
![What What](/uploads/1/2/5/8/125873880/979166513.jpg)
While Encrypting a File with a Password from the Command Line using OpenSSLis very useful in its own right, the real power of the OpenSSL library is itsability to support the use of public key cryptograph for encrypting orvalidating data in an unattended manner (where the password is not required toencrypt) is done with public keys.
The Commands to Run
Generate a 2048 bit RSA Key
You can generate a public and private RSA key pair like this:
![Rsa key generation program Rsa key generation program](/uploads/1/2/5/8/125873880/146596842.png)
openssl genrsa -des3 -out private.pem 2048
That generates a 2048-bit RSA key pair, encrypts them with a password you provideand writes them to a file. You need to next extract the public key file. You willuse this, for instance, on your web server to encrypt content so that it canonly be read with the private key.
Export the RSA Public Key to a File
This is a command that is
openssl rsa -in private.pem -outform PEM -pubout -out public.pem
The
-pubout
flag is really important. Be sure to include it.Next open the
public.pem
and ensure that it starts with-----BEGIN PUBLIC KEY-----
. This is how you know that this file is thepublic key of the pair and not a private key.To check the file from the command line you can use the
less
command, like this:less public.pem
Do Not Run This, it Exports the Private Key
A previous version of the post gave this example in error.
openssl rsa -in private.pem -out private_unencrypted.pem -outform PEM
The error is that the
-pubout
was dropped from the end of the command.That changes the meaning of the command from that of exporting the public keyto exporting the private key outside of its encrypted wrapper. Inspecting theoutput file, in this case private_unencrypted.pem
clearly shows that the keyis a RSA private key as it starts with -----BEGIN RSA PRIVATE KEY-----
.Visually Inspect Your Key Files
It is important to visually inspect you private and public key files to makesure that they are what you expect. OpenSSL will clearly explain the nature ofthe key block with a
-----BEGIN RSA PRIVATE KEY-----
or -----BEGIN PUBLIC KEY-----
.You can use less to inspect each of your two files in turn:
less private.pem
to verify that it starts with a-----BEGIN RSA PRIVATE KEY-----
less public.pem
to verify that it starts with a-----BEGIN PUBLIC KEY-----
The next section shows a full example of what each key file should look like.
The Generated Key Files
What Is Rsa Key Generation Windows
The generated files are base64-encoded encryption keys in plain text format.If you select a password for your private key, its file will be encrypted withyour password. Be sure to remember this password or the key pair becomes useless.
The private.pem file looks something like this:
The public key, public.pem, file looks like:
Protecting Your Keys
Depending on the nature of the information you will protect, it’s important tokeep the private key backed up and secret. The public key can be distributedanywhere or embedded in your web application scripts, such as in your PHP,Ruby, or other scripts. Again, backup your keys!
Remember, if the key goes away the data encrypted to it is gone. Keeping aprinted copy of the key material in a sealed envelope in a bank safety depositbox is a good way to protect important keys against loss due to fire or harddrive failure.
Oh, and one last thing.
If you, dear reader, were planning any funny business with the private key that I have just published here. Know that they were made especially for this series of blog posts. I do not use them for anything else.
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[Back] With RSA, initially the person picks two prime numbers. For example: p=11 and q=3 Try In the following you can either manually add your own values, or generate random ones by pressing the button. [Lecture][Examples] [Use your own P and Q values] [Software Tutorial] Next, the n value is calculated. Thus: n = p x q = 11 x 3 = 33 Next PHI is calculated by: PHI = (p-1)(q-1) = 20 The factors of PHI are 1, 2, 4, 5, 10 and 20. Next the public exponent e is generated so that the greatest common divisor of e and PHI is 1 (e is relatively prime with PHI). Thus, the smallest value for e is: e = 3
The factors of e are 1 and 3, thus 1 is the highest common factor of them. Thus n (33) and the e (3) values are the public keys. The private key (d) is the inverse of e modulo PHI. d=e^(-1) mod [(p-1)x(q-1)] This can be calculated by using extended Euclidian algorithm, to give d=7.
The encryption and decryption keys are then:
As a test you can manually put in p=11 and q=3, and get the keys of (n,e)=(33,3) and (n,d)=(33,7). The PARTY2 can be given the public keys of e and n, so that PARTY2 can encrypt the message with them. PARTY1, using d and n can then decrypt the encrypted message. For example, if the message value to decrypt is 4, then: [begin{align*}c = m^{e}mod{n} end{align*}] [begin{equation}c = 4^{3}mod{33} = 64mod{33} = 31 end{equation}] Therefore, the encrypted message (c) is 31. The encrypted message (c) is then decrypted by PARTY1 with: [begin{equation}m = c^dmod n = 31^{7}mod 33 = 27,512,614,111mod 33 = 4 end{equation}] which is equal to the message value. Encryption/Decryption: |
Try an example
- p=11, q=3, e=3 and message of 4. Try
- p=13, q=11, e=7 and message of 7. Try
- p=47, q=71, e=79 and message of 688, which should give a cipher of 1570. TryReference
- p=3, q=11, e=7 and message of 14, which should give a cipher of 20. TryReference
- p=11, q=3, e=3 and message of 7, which should give a cipher of 13. TryReference
- p=23, q=41, e=7 and message of 35 which should give a cipher of 545. TryReference
- p=61, q=53, e=17 and message of 65 which should give a cipher of 2790. TryReference
- p=11, q=3, e=7 and message of 2 which should give a cipher of 29. TryReference
- p=7, q=13, e=5 and message of 10 which should give a cipher of 82. TryReference
- p=11, q=13, e=7 and message of 9 which should give a cipher of 48. TryReference
Try an example that won't work
Rsa Key Generation Cisco
- p=13, q=11, e=5 and message of 7. Try. Why? Because PHI has a common factor to E that is greater than 1.