A Time-based One-time Password Algorithm (TOTP) is an algorithm that computes a one-time password from a shared secret key and the current time. It is the cornerstone of Initiative For Open Authentication (OATH) and is used in a number of two factor authentication systems. Essentially, both the server and the client compute the time-limited. I'm looking for a concrete algorithm to generate one time passwords. The situation is as follows: Alice and Bob exchanged a passphrase over a secure channel in the beginning. They want to symetrically encrypt data in the future, and every consecutive enryption/decryption process. Aug 24, 2017 Even if your password is compromised, two-factor authentication will keep them from gaining access to your accounts. 1Password, the best password manager, has built in support for two-factor authentication and one-time passwords. While you can use SMS codes, these aren’t as secure as using one-time passwords.
You can login to a remote Linux server without entering password in 3 simple steps using ssky-keygen and ssh-copy-id as explained in this article.
ssh-keygen creates the public and private keys. ssh-copy-id copies the local-host’s public key to the remote-host’s authorized_keys file. ssh-copy-id also assigns proper permission to the remote-host’s home, ~/.ssh, and ~/.ssh/authorized_keys. This article also explains 3 minor annoyances of using ssh-copy-id and how to use ssh-copy-id along with ssh-agent.
Aug 21, 2013 The authentication server can generate a one-time password and encrypt it with the public key of the user. The user is the only one, who can decrypt it, because only he knows the corresponding private key. The user decrypts the one-time password and sends it to the authentication server.
Step 1: Create public and private keys using ssh-key-gen on local-hostStep 2: Copy the public key to remote-host using ssh-copy-id
Note: ssh-copy-id appends the keys to the remote-host’s .ssh/authorized_key.
Step 3: Login to remote-host without entering the passwordThe above 3 simple steps should get the job done in most cases. We also discussed earlier in detail about performing SSH and SCP from openSSH to openSSH without entering password. If you are using SSH2, we discussed earlier about performing SSH and SCP without password from SSH2 to SSH2 , from OpenSSH to SSH2 and from SSH2 to OpenSSH. Using ssh-copy-id along with the ssh-add/ssh-agent
When no value is passed for the option -i and If ~/.ssh/identity.pub is not available, ssh-copy-id will display the following error message.
If you have loaded keys to the ssh-agent using the ssh-add, then ssh-copy-id will get the keys from the ssh-agent to copy to the remote-host. i.e, it copies the keys provided by ssh-add -L command to the remote-host, when you don’t pass option -i to the ssh-copy-id. Three Minor Annoyances of ssh-copy-id
Following are few minor annoyances of the ssh-copy-id.
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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…
EncryptingDecryptingUsing 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
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:
Openssl Change Private Key Password![]()
![]() 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:
One Time Password To Generate Private Key Blockchain
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.
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