This page attempts to explain public keys, as used in SSH, to readers unfamiliar with the concept.

The following concepts need to be understood by everyone, including beginner users:

• Mar 16, 2017 How to use/setup Bitvise Ssh client software. How to configure Bitvise ssh client software to access sftp server public key authentication using bitvise ssh client software.
• Feb 16, 2020 Bitvise SSH Client is a freeware SSH client software app filed under ssh/telnet clients and made available by Bitvise Limited for Windows. The review for Bitvise SSH Client has not been completed yet, but it was tested by an editor here on a PC and a list of features has been compiled; see below.
• The procedure for generating the keypair depends on the client software being used: If you are using Bitvise SSH Client, click the link titled Client key manager in the Login tab. If you are using a different client, you need to follow its process for generating keypairs.

• A private key is a very large, pseudo-randomly generated number, that contains your secret information in any operation involving public keys. You generate the private key on your computer, using one of a variety of programs, and store it securely. You need to keep your private key secure; you never send it to anyone.

• A public key is a very large number, mathematically derived from your private key. It is derived in such a way that the two numbers are linked, but so that the private key cannot be discovered by anyone who only knows the public key. /key-generator-for-mathematica-9.html. The public key is what you send to other parties, to whom you want to authenticate yourself, or to whom you want to send encrypted messages. The public key is not sensitive, and does not need to be protected. It is public.

• A signature is a result of a cryptographic calculation that can be performed only by a person who holds a private key, and can be verified by anyone who knows the corresponding public key. If a person is able to produce a valid signature of random data on demand, this proves that they have access to the private key associated with a particular public key.

• A keypair is the combination of the private key and the public key. A keypair by necessity includes the private key, so a full keypair ought to be protected just like a private key.

• A fingerprint is a cryptographic digest that can be used to uniquely identify a public key. Fingerprints are used for practical purposes, to compare keys which would otherwise be too large and unwieldy to compare manually. The most common fingerprint formats used in SSH are the SHA-256 format (example - 'C+VpXsf.'), the MD5 format (example - '43:71:be:ab:d3:.'), and the Bubble-Babble format (example - 'xubem-kiloc-getad-ponyh-.'). Like a public key, the fingerprint is not sensitive information, and can be disclosed indiscriminately.

• A certificate is a public key, cryptographically signed by a certification authority (CA) in a public key infrastructure (PKI). The most widely used certificate standard is X.509. In the way SSH is most commonly used, it does not support certificates. Certificates are used primarily in TLS (SSL), which is a different protocol from SSH that serves a similar purpose. Most common SSH implementations only use raw public keys and private keys.

Configuring public key authentication with Bitvise SSH Client. Public keys, in the way they are. It is private. If this is the first time you are using public keys, we recommend the page Public keys in SSH. Generate public/private keypair. To use public key authentication, the client from which you are connecting needs to have a public. Keys that are used for server authentication in SSH are displayed in the Host keys section of the Bitvise SSH Server Control Panel, and can be configured through the link Manage host keys. This section manages private keys, which are stored by the SSH server so it can authenticate itself to clients that connect to it. Bitvise is one of the few SSH clients that offers all features free for all types of users, including organizations. At the same time, there are no compromises in terms of functionality. It has an advanced GUI, corporation-wide single sign-on, learning resources including guides and FAQs, and other features. Bitvise SSH Server is an SSH, SFTP and SCP server for Windows. It is robust, easy to install, easy to use, and works well with a variety of SSH clients, including Bitvise SSH Client, OpenSSH, and PuTTY. The SSH Server is developed and supported professionally by Bitvise. You can download Bitvise SSH Server here.

SSH sessions use public keys for two main purposes: server authentication, and client authentication. Both processes work very similarly, but they involve separate sets of keys. When discussing a specific public key in the context of SSH, it is important to be aware whether the key is intended to authenticate the server, or a client.

In Bitvise SSH Server:

• Keys that are used for server authentication in SSH are displayed in the Host keys section of the Bitvise SSH Server Control Panel, and can be configured through the link Manage host keys. This section manages private keys, which are stored by the SSH server so it can authenticate itself to clients that connect to it.

  In Keypair management, you can use the Export feature to export the public key associated with each host authentication keypair. You can send such a public key to an SSH client, so it will be able to authenticate the SSH server when it connects to it. If you do not send the client the whole public key, you should at least provide the user with your server's host key fingerprint, so that the user can confirm the server's public key is correct when they see it. The server's host key fingerprints can be viewed and copied from the main screen of the Bitvise SSH Server Control Panel.

• Keys that are used for client authentication are managed through individual account settings entries. To view or configure these keys, open Easy or Advanced SSH server settings, and open a specific Windows or virtual account entry. Within this entry, find the link named 'Public keys'. This link opens a dialog which can be used to import, export, or remove public keys that the client can use to log into the server.

  The SSH server will allow a client to add or remove keys themselves if 'Allow public key management' is enabled in the user's account or group settings entry in Advanced SSH server settings, or if 'Synchronize with authorized_keys' is enabled in Advanced settings > Access control. Windows product key generator xp.

  If you are trying to configure public key authentication for a client connecting to Bitvise SSH Server, check also the Public Key Authentication section of our Bitvise SSH Server Usage FAQ.

• Since versions 8.xx, the SSH Server also supports FTPS. FTPS is a file transfer protocol which uses TLS, not SSH; and TLS does use X.509 certificates. The SSH Server Control Panel includes a Manage certificates interface which allows you to generate a self-signed certificate or a certificate signing request (CSR) to obtain an X.509 certificate from an issuer (a CA). The SSH Server uses a certificate only for FTPS, where it is used to authenticate the server to the FTPS client.

In Bitvise SSH Client:

• Public keys of hosts you have connected to can be viewed in Host key manager. When you connect to an SSH server for the first time, and the client has no record of the server's host key, the client will display the server's host key fingerprint, and will ask you to verify the key. It is very important to verify the server's host key fingerprint at this point, which should be done against a fingerprint you received through other means from the server's administrator. If you verify that the key is correct, the client will save it, and trust it for further connections to the server.

  If you do not verify the server's host key, then the client cannot verify that the server you are connecting to is in fact the server you think you are connecting to. Not verifying the server's host key enables a man-in-the-middle attack - a situation where you aren't actually connecting to the server you think you are connecting to, but rather to another server that impersonates you to the destination server, and the destination server to you. Such a man-in-the-middle is able to observe all data sent over the SSH session, as well as modify what's being sent in real time. The only way to defend against such an attack is to make sure to verify the server's host key.

• Private keys used for client authentication can be generated, imported and exported in User keypair manager. This interface allows you to generate a keypair for client authentication; you should keep the private key that's part of this keypair private. You can use the Export function to export the public key portion of a keypair, and send it to a server administrator, who can import it to allow you to authenticate using that key. The only thing you need to send to the server administrator is the public key; you should never send the private key, or the whole keypair.

Properly verified host keys are essential to the security of the SSH protocol. Many clients exist which do not verify a host key. This happens especially with clients which originally support different protocols, and add SSH as yet another one to support. Such clients are not secure to use.

If the client does not verify the server's host key, it renders the connection vulnerable to a man-in-the-middle attack. This means that anyone who is in a network position between the client and the server - including an ISP, or a hacker that gained control of a network gateway - can modify the connection in such a way as to observe, modify, or inject any and all sensitive information without being noticed.

A host key is verified by a client as follows: download emulator android untuk mac

• The client might be configured with the full public key, or several public keys, corresponding to host keys used by the server. When the client connects, it verifies that the server is using one of these host keys.

• The client might be configured with one or more host key fingerprints it should expect from the server. A host key fingerprint is a cryptographic digest of the public key portion of the host key. The fingerprint is calculated using a hash function such as SHA-256, SHA-1, or MD5. Due to weaknesses in SHA-1 and MD5, the type of fingerprint which is now most recommended is SHA-256.

• The client might not be configured with a host key, or might expect a different host key than is received from the server. In this case, a secure client must either prevent the connection, or require the user to verify the fingerprint of the received host key.

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For more information about how public keys are used in SSH, for both server and client authentication, we recommend the page Public keys in SSH.

Bitvise SSH Server can use multiple host keys - one for each different host key algorithm. Supported host key algorithms include RSA, Ed25519, several ECDSA algorithms, and the legacy DSA host key algorithm.

When a client connects to Bitvise SSH Server, the host key that will be used is determined as follows:

• The SSH Server sends a list of host key algorithms for which it has host keys that are employed.

• The client sends a preference list of host key algorithms it supports. Depending on the client, this might be a list of all host key algorithms the client supports, including algorithms for which the client does not trust any host key for this server. Alternately, this could be a list of only those host key algorithms for which the client does know a trusted host key for this server.

• The host key algorithm that is chosen is the first algorithm named by the client which is also named by the server.

An administrator may wish to add or replace one or more host keys of an existing SSH Server instance for reasons such as:

• The SSH Server may be using an older type or size of key that is no longer recommended in SSH. For example: we recommend replacing any size of DSA host key, and any RSA key smaller than 2048 bits, with a 3072-bit RSA host key.

• An existing host key could have been exposed to compromise. For example, an administrator might have exported the private key for backup, and there were insufficient controls on the backup to ensure it wasn't accessed in an unauthorized way.

• Replacement might be mandated by a key rollover policy.

For example, an administrator may wish to replace a 1024-bit RSA host key with a 3072-bit RSA key. The new host key will have a different public key and a different fingerprint which existing clients do not trust. To replace this host key, we recommend the following process:

• Generate a new host key using the Manage host keys interface in the SSH Server Control Panel, but do not yet employ the key.

• Distribute either the full new public key, or fingerprints of the new host key, to all clients that need to connect to the SSH Server. Do not send the private key to anyone!

• Provide client administrators sufficient time to configure trust in the new host key. At this time, previously employed host keys continue to be used for connections.

• Once all clients have been configured to accept the new host key, employ the new host key in place of the old one.

The old host key of the same algorithm can be kept in the Manage host keys interface in dismissed status, and/or can be removed at the administrator's convenience.

For example, an administrator may wish to add a 3072-bit RSA host key to a system that already uses a 1024-bit DSA host key, and has clients trusting the 1024-bit key.

In this case, in theory, the administrator could simply add the new RSA host key, employ it, and leave the DSA host key in place, allowing clients to migrate to the new RSA host key over time.

In practice, however, this will only work if all existing clients that trust the DSA host key either:

• do not support the RSA host key algorithm at all; or

• their host key algorithm preference list puts DSA in front of RSA; or

• no client will request RSA as more preferred than DSA in a situation where it only trusts a DSA key, but not an RSA key.

In practice, when clients connect with a variety of software, all of these conditions may be broken. For example, most clients will support the RSA host key algorithm, and many may prefer it to DSA. In addition, clients that prefer RSA to DSA will send a preference list that prefers RSA even if they trust only a DSA host key for this server, and do not trust any RSA host key.

As a result, with many clients, connections may break immediately as soon as an RSA host key is employed. This can happen even if there is no other reason these clients could not continue to trust the DSA host key that they have always trusted.

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For this reason, adding a new host key with a different algorithm needs to follow the following process:

• Generate a new host key using the Manage host keys interface in the SSH Server Control Panel, but do not yet employ the key.

• Distribute either the full new public key, or fingerprints of the new host key, to all clients that need to connect to the SSH Server. Do not send the private key to anyone!

• Provide client administrators sufficient time to configure trust in the new host key.

• Once all clients have been configured to accept the new host key, employ the new host key.