17.12.2020

Generate Public Key Mac Terminal

Generate Public Key Mac Terminal Rating: 7,1/10 3835 reviews

However, you can follow the same process to use a private key when using any terminal software on Linux. Note: For information about using Secure Shell (SSH) private keys on Microsoft® Windows® operating systems, see Logging in with an SSH Private Key on Windows and Generate RSA keys with SSH by using PuTTYgen. Nov 10, 2011 If you are using SSH frequently to connect to a remote host, one of the way to secure the connection is to use a public/private SSH key so no password is transmitted over the network and it can prevent against brute force attack. In Linux, creating a public/private SSH key is easy. Open a terminal. Generate Your Keypair. If you’re using Transmit 5, Code Editor, Transmit for iOS, or Prompt, you can generate keypairs from inside the app. If you’re on a Mac, we can generate your keypair from the command line. Open a Terminal window and enter the following command: $ ssh-keygen -t rsa -b 4096. PuTTYgen is a key generator tool for creating pairs of public and private SSH keys. It is one of the components of the open-source networking client PuTTY. Although originally written for Microsoft Windows operating system, it is now officially available for multiple operating systems including macOS, Linux.

This guide will demonstrate the steps required to encrypt and decrypt files using OpenSSL on Mac OS X. The working assumption is that by demonstrating how to encrypt a file with your own public key, you'll also be able to encrypt a file you plan to send to somebody else using their private key, though you may wish to use this approach to keep archived data safe from prying eyes.

Too Long, Didn't Read

Assuming you've already done the setup described later in this document, that id_rsa.pub.pcks8 is the public key you want to use, that id_rsa is the private key the recipient will use, and secret.txt is the data you want to transmit…

Encrypting

Decrypting

Using Passwords

OpenSSL makes it easy to encrypt/decrypt files using a passphrase. Unfortunately, pass phrases are usually 'terrible' and difficult to manage and distribute securely.

To Encrypt a File

You can add -base64 if you expect the context of the text may be subject to being 'visible' to people (e.g., you're printing the message on a pbulic forum). If you do, you'll need to add it to the decoding step as well. You can choose from several cypers but aes-256-cbc is reasonably fast, strong, and widely supported. Base64 will increase the size of the encrypted file by approximately 30%

To Decrypt a File

You will need to provide the same password used to encrypt the file. All that changes between the encrypt and decrypt phases is the input/output file and the addition of the -d flag. If you pass an incorrect password or cypher then an error will be displayed.

Encrypting Files Using your RSA keys

RSA encryption can only work with very short sections of data (e.g. an SHA1 hash of a file, or a password) and cannot be used to encrypt a large file. The solution is to generate a strong random password, use that password to encrypt the file with AES-256 in CBC mode (as above), then encrypt that password with a public RSA key. The encrypted password will only decrypt with a matching public key, and the encrypted file will require the unique password encrypted in the by the RSA key.

Replace OpenSSL

The copy of OpenSSL bundled with Mac OS X has several issues. Mac OS X 10.7 and earlier are not PCI compliant. It is best to replace it. See here for details: http://www.dctrwatson.com/2013/07/how-to-update-openssh-on-mac-os-x/

Generate Your Private/Public Key-pair

By default your private key will be stored in

  • ~/.ssh/id_rsa : This is your private key and it must be kept secret
  • ~/.ssh/id_rsa.pub : This is your public key, you can share it (for example) with servers as an authorized key for your account.You can change the location of where you store your keys, but this location is typical. Typically you want to ensure the private key is chmod 600, andd the public key is chmod 644.

Generate a PKCS8 Version of Your Public Key

The default format of id_rsa.pub isn't particularly friendly. If you are going to public your key (for example) on your website so that other people can verify the authorship of files attributed to you then you'll want to distribute it in another format. I find it useful to keep a copy in my .ssh folder so I don't have to re-generate it, but you can store it anywhere you like.

Generate a One-Time-Use Password to Encrypt the File

The passwords used to encrypt files should be reasonably long 32+ characters, random, and never used twice. To do this we'll generate a random password which we will use to encrypt the file.

This will generate 192 bytes of random data which we will use as a key. If you think a person may need to view the contents of the key (e.g., they're going to display it on a terminal or copy/paste it between computers) then you should consider base-64 encoding it, however:

  1. The password will become approximately 30% longer (and there is a limit to the length of data we can RSA-encrypt using your public key
  2. The password will be 'padded' with '=' characters if it's not a multiple of 4 bytes.

A Note on Long Passwords

There is a limit to the maximum length of a message that can be encrypted using RSA public key encryption. If you want to use very long keys then you'll have to split it into several short messages, encrypt them independently, and then concatinate them into a single long string. Decrypting the password will require reversing the technique: splitting the file into smaller chuncks, decrypting them independently, and then concatinating those into the original password key file.

Encrypt the File Using the Generated Key

Now that you have a good random password, you can use that to AES encrypt a file as seen in the 'with passwords' section

Decrypting the file works the same way as the 'with passwords' section, except you'll have to pass the key.

Encrypt the Key Used to Encrypt the File

We used fast symetric encryption with a very strong password to encrypt the file to avoid limitations in how we can use asymetric encryption. Finally, we'll use asymetric encryption to encrypt the password. This solves the problem of 'how do I safely transmit the password for the encrypted file' problem. You can encrypt is using the recipients public key and they can decode it using their private key. Encrypt the password using a public key:

The recipient can decode the password using a matching private key:

Package the Encrypted File and Key

There are a number of ways to do this step, but typically you'll want just a single file you can send to the recipent to make transfer less of a pain. I'd recommend just making a tarball and delivering it through normal methods (email, sftp, dropbox, whatever). Though a secure method of exchange is obviously preferable, if you have to make the data public it should still be resistent to attempts to recover the information.

The file can be extracted in the usual way:

You may want to securely delete the unecrypted keyfile as the recipient will be able to decode it using their private key and you already have the unencrypted data.

Real talk: passwords are bad. Passwords are notoriously hard to remember, yet easy for attackers to break. A secure password is a long, meaningless string containing a mix of letters, numbers, and symbols. Because they’re so hard to remember, it’s tempting to use the same password everywhere, which means you have to change all your passwords if just one login gets compromised.

Fortunately for us, SSH allows connections to be authenticated using keys. Key-based authentication is a huge improvement over a simple username and password combination.

Instead of a password, you have a pair of matched keys: one public, and one private. Anyone with access to the public key can use it to encrypt information, which can only be decrypted using the corresponding private key.

First, we need some keys to use.

Did your server provide you with keys?
Great! Let’s skip down a bit.
Don’t have any keys?
Not to worry, we can generate them.

Generate Your Keypair

If you’re using Transmit 5, Code Editor, Transmit for iOS, or Prompt, you can generate keypairs from inside the app.

If you’re on a Mac, we can generate your keypair from the command line. Open a Terminal window and enter the following command:

The $ symbol indicates a command prompt. Everything after the $ is a command to be entered.

Press Return, and you’ll see this:

The first decision to make is where to keep your key, and what to call it. For now we’ll just stick with the defaults.

Hit Return to create a keypair using the default name id_rsa and put it in the .ssh folder in your home folder.

Nerd Stuff! The Finder in macOS keeps that .ssh folder hidden. To see your .ssh folder in the Finder, press Command+Shift+G, then enter ~/.ssh. Also! The tilde (~) is filesystem shorthand for your user’s home folder. So when we say ~/.ssh, that means /Users/YOU/.ssh.

Next you can opt to encrypt your private key with a passphrase.

The passphrase is an extra layer of security on your private key. With a passphrase, not only does someone need to gain access to your private key, they also need your passphrase in order to make use of it.

To set a passphrase, enter it here.

To skip setting a passphrase, hit Return without typing anything.

Whether you set a passphrase or not, you’ll be asked to confirm it. Enter the passphrase again, or just press Return.

Your keypair has been generated.

Note that the private key is called “id_rsa” and the public key is “id_rsa.pub”, and they’re both in a folder called “.ssh” in your home folder.

The Public Key

The public key (the one ending in .pub) goes on the remote server. If your server administrator provided you with a key to use, they’ve likely already taken care of this for you. If not, you’ll need to find a way to put your public key on the server.

In most cases, this means connecting with a username and password. Once connected, navigate into ~/.ssh/ on the remote server and look for a file called authorized_keys or authorized_keys2. Open that file in a text editor, and append the entire contents of your public key onto the end of the file.

Your public key is a text file with a single long line. Enter this command to see it:

It should look like this:

Generate crypto key cisco for ssh. Note:This is just an example. This is not a valid public key.

The Private Key

The private key stays private. The .ssh folder in your home folder is a good place to keep it. Enter this command to see it:

Your private key should look something like this:

Note:This is just an example. This is not a valid private key.

The ~/.ssh/config File

Along with your public and private keys, your .ssh folder can contain a file called config containing settings and preferences relating to your keys and servers. There are too many possible options to list here, and not every possibility is supported (or even practical) in every app.

You may need to create the config file if it doesn’t already exist.

As a basic example, here’s what you’d put in your config so that the key called exampleKey is used when connecting with the username user to the server example.com.

This is a great way to tell apps which key file goes with which server, especially if you use non-standard names for your keys, you keep your keys outside of ~/.ssh, or if you use passphrase-encrypted keys, which Coda and Transmit cannot validate.

You probably won’t ever need to touch your config file. There are a handful of special-snowflake situations where setting an option in the config file is the only way to make it work. Your server administrator can guide you if problems arise.

Though all of our apps offer some level of support for key-based authentication, there are some differences from app to app in how keys are handled.

Supported Formats

Generally, our apps support ECDSA, RSA and DSA keys in PEM format.

Transmit 5 and Prompt 2 have additional support for Ed25519, ECDSA, RSA and DSA keys in OpenSSH format.

OpenSSH has deprecated the DSA public key algorithm due to its inherent weakness. DSA keys are disabled by default in macOS Sierra. We strongly recommend against using DSA keys if possible.

PuTTY/PPK

Keys in the PuTTY format (PPK) are not supported. If you have a PuTTY key, you can convert it to OpenSSH/PEM by following these instructions under the Dealing with Private Keys in Other Formats section.

The Present

We’re using an SSH library based on libssh2 and OpenSSL. This library, used in Transmit 5, Coda 2, Prompt, Transmit iOS, and Code Editor, currently supports the following:

KexAlgorithms
diffie-hellman-group-exchange-sha1
diffie-hellman-group14-sha1
diffie-hellman-group1-sha1
diffie-hellman-group-exchange-sha256
ecdh-sha2-nistp256
ecdh-sha2-nistp384
ecdh-sha2-nistp521
Ciphers
aes128-ctr
aes192-ctr
aes256-ctr
aes128-cbc
aes192-cbc
aes256-cbc
blowfish-cbc
arcfour
arcfour128
cast128-cbc
3des-cbc
MACs
sha2-512-etm@openssh.com
sha2-512
sha2-256-etm@openssh.com
sha2-256
sha1
sha1 96
ripemd160

Beyond what libssh2 includes, we’ve added support for ECDSA and EtM. We’ll continue to refine and improve this library, and push our changes to the upstream libssh2 project.

Legacy releases

Transmit 4 and Coda 1 used the OpenSSH library built-in to Mac OS X. This means key support in Transmit 4 and Coda 1 is limited to what the OS-provided library supports.

Host Key Verification

The first time you connect to a server, we keep a local copy of the key the server uses to identify itself. On future connections, we can use this stored key to verify that the server we’re connecting to now is the same one we’ve connected to before. Without host key verification, we’d be vulnerable to man-in-the-middle attacks.

If an app warns that the host key has changed, it means this server’s key looks different from the key we stored the first time we connected to this server. If this is unexpected, you should reject the changed key, cease connecting to this server, and contact your server administrator.

In Transmit (version 5 and later), Code Editor and Prompt, the host key fingerprint is displayed the first time you connect to a new server.

In Coda, Transmit iOS, and older versions of Transmit, the host key is blindly accepted on first connection. This is generally fine, but it’s something to be aware of if you’re on an untrusted local network.

To view the host key fingerprint used in Coda or Transmit, open the file ~/.ssh/known_hosts and find the line that corresponds to your server. If you need to reset the host key for a server, just remove the entire line for that server from the known_hosts file.

In Code Editor and Prompt, you can view the fingerprint at any time from the server settings.

Advanced Features

Prompt and the terminal in Code Editor support agent forwarding. Coda, Transmit, and Transmit iOS do not.

Port forwarding, X11 forwarding, and ProxyCommand are not currently supported.

App-Specific Notes

Coda

In the Server pane of Coda’s Site configuration sheet, there is a button with a key icon to the right of the password field. This button opens a file picker that allows you to choose a private key to use when connecting to this server. Coda automatically attempts to use any keys it finds in your .ssh folder.

When choosing a key via this button, Coda will attempt to verify the format of the key to make sure that it’s valid and supported.

If your key is encrypted with a passphrase, Coda’s key-chooser will be unable to verify it. See the config file workaround above.

If you’ve specified an encrypted key for use with this server in your config file, you can leave the key button alone and put the passphrase in Coda’s password field.

The Terminal, Source Control, and MySQL functions in Coda also support keys, but you will need to add your key to the config file.

Transmit 5

In the latest version of Transmit we’ve added the ability to store keys right in Transmit itself. Additionally, Transmit 5 still supports keys defined in in your config file.

For a more comprehensive overview of the many ways Transmit 5 can be configured to use key-based authentication please see Transmit 5 SFTP Authentication.

Transmit 4

When connecting to an SFTP server, there is a button with a key icon to the right of the password field. This button works in much the same way as the same button in Coda: it opens a file picker that allows you to choose a private key for use when connecting to this server. Transmit will automatically attempt to use any keys it finds in your .ssh folder.

When choosing a key via this button, Transmit will attempt to verify the format of the key to make sure that it’s valid and supported.

If your key is encrypted with a passphrase, Transmit’s key-chooser will be unable to verify it. See the config file workaround above.

If you’ve specified an encrypted key for use with this server in your config file, you can leave the key button alone and put the passphrase in Transmit’s password field.

Prompt

When creating a new server connection, tap the key icon next to the password field to choose a private key. If the key is encrypted with a passphrase, you can enter it when choosing the key. If you do not enter the passphrase, you will be prompted for it whenever you connect to this server.

Important! If you want to use a key with a passphrase for agent forwarding, you must enter the passphrase when adding the key to the server connection.

You can view, import, and create keys in the Keys pane of Prompt’s Settings.

To add a key for use in Prompt, open the Settings pane, tap Keys, then tap the + button at the top right of the Keys pane. You can choose to either Generate a new key, or Import an existing key.

Generate New Key

To generate a new key, tap the + button on the Keys pane of Prompt’s settings and choose Generate New Key. Choose a descriptive name for your key, and optionally set a passphrase. Choose your key type, and size. Then tap “Generate” to create your keypair. Once it’s finished generating, tap Copy Public Key to put the public key on your pasteboard. We’ll use it in the next step.

Now that you have your keypair, you’ll want to put the public key on the remote server. Usually this means this means connecting with a username and password one last time. Once connected, navigate into ~/.ssh/ on the remote server and look for a file called authorized_keys or authorized_keys2. Open that file in a text editor, and paste the public key onto the end of the file.

Copy from Clipboard

To import a key from the iOS Clipboard, first select and copy the entire contents of the private key to the pasteboard. After the private key is on the Clipboard, go to Prompt’s Settings, tap Keys, then tap the + button and choose Copy from Clipboard. If your key is in a valid and supported format – and if it’s the private key, not the public key – Prompt will import the key for you.

Import from iTunes

Use iTunes File Sharing to import your private key. Note that Prompt does not support importing arbitrary files via iTunes File Sharing; this only works for keys.

Agent Forwarding

To enable agent forwarding in Prompt, toggle the Agent Forwarding switch in the Server settings. If your key uses a passphrase, you’ll need to have entered it when you added the key to the server entry.

Code Editor

When creating a remote server connection in a new Site, tap the key icon next to the password field to choose a private key. If the key is encrypted with a passphrase, you can enter it when choosing the key. If you do not enter the passphrase, you will be prompted for it whenever you connect to this server.

Important! If you want to use a key with a passphrase for agent forwarding, you must enter the passphrase when adding the key to the server connection.

You can view, import, and create keys in the Keys pane of Coda’s Settings.

To add a key for use in Coda, open the Settings pane, tap Keys, then tap the + button at the top right of the Keys pane. You can choose to either Generate a new key, or Import an existing key.

Generate New Key

To generate a new key, tap the + button on the Keys pane of Coda’s settings and choose Generate New Key. Choose a descriptive name for your key, and optionally set a passphrase. Choose your key type, and size. Then tap “Generate” to create your keypair. Once it’s finished generating, tap Copy Public Key to put the public key on your pasteboard. We’ll use it in the next step.

Now that you have your keypair, you’ll want to put the public key on the remote server. Usually this means this means connecting with a username and password one last time. Once connected, navigate into ~/.ssh/ on the remote server and look for a file called authorized_keys or authorized_keys2. Open that file in a text editor, and paste the public key onto the end of the file.

Import From Pasteboard

To import a key from the iOS Pasteboard, first select and copy the entire contents of the private key to the pasteboard. After the private key is on the pasteboard, go to Coda’s Settings, tap Keys, then tap the + button and choose Import from Pasteboard. If your key is in a valid and supported format – and if it’s the private key, not the public key – Coda will import the key for you.

Import from Local

Use this option to import a private key from the Local file storage on your iOS device. One example where this is useful is if you’ve got your private key on your Mac. Use Coda to connect to your Mac on the same local network, then transfer the key into Coda’s Local file storage. Once the key is in Coda’s local file storage, it can be imported for use.

Import from iTunes

Use iTunes File Sharing to import your private key. Note that Coda does not support importing arbitrary files via iTunes File Sharing; this only works for keys.

Agent Forwarding

To enable agent forwarding in Code Editor, toggle the Agent Forwarding switch in the Terminal pane of the Site’s settings. If your key uses a passphrase, you’ll need to have entered it when you added the key to the server entry.

Transmit iOS

When creating a new server connection, tap the key icon next to the password field to choose a private key. If the key is encrypted with a passphrase, you can enter it when choosing the key. If you do not enter the passphrase, you will be prompted for it whenever you connect to this server.

You can view, import, and create keys in the Keys pane of Transmit’s Settings.

To add a key for use in Transmit, open the Settings pane, tap Keys, then tap the + button at the top right of the Keys pane. You can choose to either Generate a new key, or Import an existing key.

Generate New Key

To generate a new key, tap the + button on the Keys pane of Transmit’s settings and choose Generate New Key. Choose a descriptive name for your key, and optionally set a passphrase. Choose your key type (we recommend RSA), and size (we recommend 2048 or 4096). Then tap “Generate” to create your keypair. Once it’s finished generating, tap Copy Public Key to put the public key on your pasteboard. We’ll use it in the next step.

Now that you have your keypair, you’ll want to put the public key on the remote server. Usually this means this means connecting with a username and password one last time. Once connected, navigate into ~/.ssh/ on the remote server and look for a file called authorized_keys or authorized_keys2. Open that file in a text editor, and paste the public key onto the end of the file.

Generate Ssh Key Mac Command Line

Import From Pasteboard

To import a key from the iOS Pasteboard, first select and copy the entire contents of the private key to the pasteboard. After the private key is on the pasteboard, go to Transmit’s Settings, tap Keys, then tap the + button and choose Import from Pasteboard. If your key is in a valid and supported format – and if it’s the private key, not the public key – Transmit will import the key for you.

Generate Public Key Mac Terminal 1

Import from Local

Use this option to import a private key from the Local file storage on your iOS device. One example where this is useful is if you’ve got your private key on your Mac. Use Transmit to connect to your Mac on the same local network, then transfer the key into Transmit’s Local file storage. Once the key is in Transmit’s local file storage, it can be imported for use in Transmit.

Generate Public Key Mac Terminal 3

Import from iTunes

Use iTunes File Sharing to import your private key. Note that Transmit does not support importing arbitrary files via iTunes File Sharing; this only works for keys.

Troubleshooting

Why does it say my key is not in a supported format?

The most common reason you’d see this error is if you select a passphrase-encrypted key via the key chooser button in either Coda or Transmit on macOS. Coda and Transmit want to validate the key before letting you use it, but the encryption prevents that from happening. (Admittedly, this is not ideal, and should be improved.)

As a workaround, add your key to the ~/.ssh/config file, skip the key button altogether, and put the passphrase in the password field.

You’ll also get this error if you use a key in an unsupported format, such as a PuTTy key. Make sure you’re using a supported key.

Why can’t I import my key from the pasteboard?

Most of the time this is a format issue. Are you sure you’re using a supported key?

Double-check that it’s the private key, not the public key. They look different (see the abovesections on each), so it should be easy to tell.

One particularly nasty gotcha to watch out for involves the text substitution feature of macOS. For example, let’s say you copy and paste the contents of your private key somewhere easily accessible from your iOS device. You might notice that macOS has helpfully changed runs of hyphens (----) into em-dashes (––).

Your private key used to look like this:

Symmetric Key

But it now looks like this:

Generate Public Key Mac Terminal 1

It’s a subtle difference, but it’s enough to break your key. Watch out!