---
title: SSH Key Registration and Management
description: "## Purpose This procedure enables secure login to a host in the cloud using SSH **public key authentication** by performing the following steps: **create public and private keys** → **register the public key in the cloud** → **verify login with…"
url: "https://bestnetllc.co.jp/en/docs/ssh-key-registration-and-management/"
updated: "2026-06-28"
category: "BESTNET-CLOUD"
---

# SSH Key Registration and Management

## Purpose

This procedure enables secure login to a host in the cloud using SSH **public key authentication** by performing the following steps: **create public and private keys** → **register the public key in the cloud** → **verify login with the private key**.

## About Public Keys and Private Keys

A public key (Public Key) and a private key (Private Key) are a **key pair** used for encryption and authentication. The public key can be shared, while the private key must be managed securely by the owner alone.

### Characteristics of Public Key (Public Key)

- **Can be shared:**There is no problem distributing it to anyone.
- **Primary uses:**
  - Encryption (data encrypted with a public key can only be decrypted with the corresponding private key)
  - Signature verification (content signed with a private key can be verified with the public key)

### Characteristics of Private Key (Private Key)

- **Absolutely confidential:**Do not share with others. If it is leaked, it can lead to unauthorized access and other issues.
- **Primary uses:**
  - Decryption (decryption of data encrypted with a public key)
  - Signing (creation of digital signatures)

## Creating Public and Private Keys (Tera Term)

Here, we will create a public key and a private key using Tera Term’s key generation function. A bit length of **4096** is recommended.

### Creation Steps

    1 Start Tera Term.     2 If a new connection popup appears after startup, close it by clicking **[Cancel]** or **[×]**.

![New connection popup immediately after Tera Term startup](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵①.png)
Figure 1: Close the popup that appears at startup

    3 Click **[Setup(S)]** from the menu at the top of the screen.

![Tera Term setup menu](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵②.png)
Figure 2: Open [Setup(S)]

    4 Click **[SSH Key Generation(N)]** (this is where you generate the key pair).

![SSH key generation menu](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵③.png)
Figure 3: Open SSH key generation

    5  On the key generation screen, set the key type to **RSA** and the bit length to **4096**, then click **[Generate(G)]** in the upper right.

![RSA 4096bit key generation screen](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵④.png)
Figure 4: Generate key with RSA (4096bit)

    6  After key generation, if a passphrase input prompt appears for private key protection, set it.

Recommended: **10 characters or more**, including **uppercase and lowercase letters**, **numbers**, and **symbols**.
 ※Creation is possible without setting a passphrase, but it is advisable to set one.

![Private key passphrase setting screen](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵⑤-1.png)
Figure 5: Set a passphrase for the private key

    7  Click the save buttons for **public key and private key** respectively on the screen to save the key files.

※If save format options (such as bcrypt KDF) are displayed on the screen, select them according to the guidance and operational rules.

※Save the **key pair (public key and private key) as a set** created from the same generation operation.

     8  In Explorer, verify that the public key and private key have been saved (for example, private key `id_rsa` / public key `id_rsa_pub`).

![Screen showing that public and private key files have been saved](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵⑥.png)
Figure 6: Verify that the two key files have been saved

### Security Precautions

- **Never share** the private key (for example, `id_rsa`).
- Avoid email attachments, chat pasting, and shared folder storage; keep it in a location with restricted access.
- If you set a passphrase, manage it safely so you do not forget it.

## Register Public Key in Cloud

The created key is not yet linked to the cloud (host), so it cannot be used as is. Here, we will **register the public key in the cloud** and apply it to the host.

### Registration Steps

    1  Log in to [cloud](https://hb.bestnetllc.co.jp/index.php?/) and navigate to **[Security]** from the menu.

![Cloud screen security menu](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵6.1-1.png)
Figure 7: Open [Security]

    2 When displayed, navigate to the **[SSH Key]** section.

![Screen for opening SSH key section](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵6.2-1.png)
Figure 8: Open [SSH Key]

    3 On the SSH Key list screen, click **[Add New SSH Key]**.

![Screen for adding a new SSH key](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵6.3-1.png)
Figure 9: Add a new SSH key

    4  When a popup appears, enter the following and click **Submit**.

- **SSH Key Name (optional)**
- **Full text of the public key** (open the public key file `id_rsa_pub`, copy all its contents, and paste it)

※If format instructions (such as OpenSSH format) appear on the screen, follow the instructions for input.

**★ The 3 golden rules for pasting your public key (this is the most common place people get stuck)**

- **① Paste the public key (not the private key).** What you paste is the public key with the `.pub` extension. Never paste your private key (such as `id_rsa`).
- **② Paste it as a single line.** The public key is a **single line** of text that begins with `ssh-rsa`. **Do not insert any line breaks** in the middle (if a line break gets mixed in, the connection will fail even if registration succeeds).
- **③ Copy the entire text.** **Open the public key file in a text editor such as Notepad**, then press `Ctrl+A` (Select All) → `Ctrl+C` (Copy). Paste everything from the leading `ssh-rsa` to the trailing comment, with no missing characters or extra whitespace.

Example of the correct format (in reality it is a single line and much longer than this):

 ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABgQC8q1m…(truncated; continues on one line)…7n3v2Q== user@example

※ If you created your key with **PuTTY**, copy and paste the string (single line) from the “**Public key for pasting into OpenSSH authorized_keys file**” box at the top of the PuTTYgen screen. **The file saved via “Save public key” uses a different format and cannot be registered as-is.**

![Popup screen for registering public key](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵6.4-1.png)
Figure 10: Register SSH key (public key)

    5  Once registration is complete, navigate to the host you want to set up and click **[Reset SSH Keys]**.

![Screen to click Reset SSH Keys](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵6.7-1.png)
Figure 11: Apply public key to host (Reset SSH Keys)

    6  When a popup appears, select the **SSH Key name** you set earlier from the dropdown menu and click **Submit**.

It may take a few minutes for the change to take effect. Once the status is **On**, the setup is complete.

![Screen for selecting and applying SSH key](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵6.6-1.png)
Figure 12: Select SSH key and confirm application is complete

## Login with Private Key (Operation Verification)

Once the public key has been linked, finally verify that you can log in with the private key.

### Login Steps

    1  Start Tera Term, enter the **IP address** in the host field and click **OK**. Select **SSH** for the service.

![Screen to start SSH connection to host in Tera Term](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵⑦.png)
Figure 13: Start SSH connection to host

    2  On the authentication screen, check **[Use RSA/DSA/ECDSA/ED25519 key]** for the authentication method. A field to specify the private key file will appear, so click the browse button.

![Screen to select key authentication and specify private key file](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵⑧-1.png)
Figure 14: Select key authentication and specify private key file

    3 Select and open the private key file (for example, `id_rsa`).

![Screen for selecting private key file](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵⑨-1.png)
Figure 15: Select private key file

    4  Once you have linked the private key, enter the **user name** and **passphrase**.

※Enter the passphrase you set when creating the key. After entering it, click **OK**.

![Authentication screen to enter user name and passphrase](https://bestnetllc.co.jp/wp-content/uploads/2025/12/公開鍵⑩-1.png)
Figure 16: Authenticate with user name and passphrase

    5 If you log in without any issues, the setup is complete.

## When it does not work / you cannot connect (checklist)

“I registered it but cannot connect,” “I get an error during registration”—most of these come down to one of the following. Check them in order from the top.

- **Did you paste the public key (.pub)?** If you paste the private key, registration and connection will fail.
- **Did you paste it as a single line?** Make sure no line breaks or extra whitespace got mixed in (one continuous line from `ssh-rsa` to the end).
- **Did you paste the entire text?** Check that neither the leading `ssh-rsa` nor the end is missing.
- **Did you run [Reset SSH Keys]?** Simply registering the public key does not apply it to the host. Run it on the target host and wait a few minutes until the status turns **on**.
- **Did you specify the correct private key on the connecting side?** Make sure you selected the private key that is the **pair** of the registered public key.
- **Is the passphrase correct?** Enter the one you set when creating the key.

**You see “Permission denied (publickey)”** → This is caused by one of the items above. In particular, “a line break got mixed in,” “you pasted the private key,” and “Reset SSH Keys was not run” are the most frequent culprits.

**You forgot the passphrase** → A private key cannot be recovered. Recreate the key pair and re-register the new public key.

If that still does not resolve the issue, please contact us via a [support ticket](https://bestnetllc.co.jp/en/docs/opening-a-ticket/).