SSH (Secure shell) is a protocol for secure communication between computers to execute remote commands, transfer data and tunnel TCP connections.

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What is the impact of RSA key's size on CPU load?

I use ssh connection encrypted and compressed. If I use small RSA keys or very big RSA keys, what is impact on CPU load for compression, for decompression and on bandwidth (encrypted file size) ?
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79 views

How to mitigate the risk of X forwarding?

I want to use X forwarding in my work because some tasks are just easier with GUI. I trust the administrators not to be malicious, but I don't trust their competence in security (almost nil). Hence ...
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2answers
12k views

Creating user specific authentication methods in SSH

I have configured sshd on an Ubuntu server to use key authentication and it is working fine. I had to disable password authentication for key authentication to work. Server is always accessed via ...
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5answers
430 views

SSH server: What's more secure, pub key auth or Google Authenticator time-based auth?

I'm curious which would be more secure, pub key authentication or 2-factor auth via Google Authenticator. Apparently I can't use both. If I have pub key authentication, the Google Auth PAM module ...
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2answers
2k views

Pros/Cons to OpenVPN vs “VPN over OpenSSH”

What are the major differences between using OpenVPN and using VPN over OpenSSH? Does adding a virtual tunnel interface to a SSH connection offer the same benefits of OpenVPN? Can PuTTY be used on ...
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1answer
2k views

Shall I set “RSAAuthentication yes” in sshd_config if I use only ECDSA key?

In a context of proprietary client boxes and servers, I want to limit authentication to ECDSA keys. Historically, "RSAAuthentication yes" was used to enable authentication with RSA and maybe DSA keys. ...
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1answer
272 views

How does Putty derive the encryption key in its .ppk format?

I have been doing some reading on the mechanics of managing RSA key pairs, during which I learned that OpenSSL by default derives the encryption key by using MD5 on the passphrase (bad!) without any ...
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1answer
73 views

SSH key passphrase update and multiply locations

I have a ssh key which I use to upload code to github. the private key is located on several locations from where I upload/download data. I wonder how can I update (or expire) old keys after I update ...
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63 views

User-friendly public/private manual authentication protocol

I have a remote service which allows users to SSH login to the machine and they're automatically sent to the (command line) application (without access to a bash prompt, for instance). In the course ...
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1answer
204 views

Difference between sshv1 and 1.5?

I've been searching for the answer to this but haven't had much luck. What is the difference between SSH version 1 and 1.5? Is 1.5 a release of 1? As in 1.2, 1.3, 1.4, 1.5? Are there any ...
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3answers
4k views

Why is using SSH key more secure than using passwords?

If people use password to log in to a UNIX server, then it could be forced to expire the password, then they change it. If people use ssh key and have no passwords, no password expirity, then ...
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2answers
102 views

OTP vs. Keyfile

I have been wondering what are the benefits and cons of using an OTP (one time password) versus a keyfile to, for example, decrypt a keepass database, connect to a server via SSH, or other uses. ...
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263 views

How compromised should I assume my computer is?

I had turned ssh on a while ago to do some remote work. I was just looking over some netstat info when I noticed someone had established an ssh session with me D: I turned ssh off immediately and ...
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How does the ShellShock exploit work over OpenSSH?

The three options listed in the CERT release (AcceptEnv TERM and SSH_ORIGINAL_COMMAND) are all server-side options. If none of these are set on a host (and no http vector is available) is the host ...
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1answer
54 views

Period and direction of risk when connecting to malicious webserver

Please forgive my terminology mishaps. Recently, I tried to connect to a server over SFTP. The SSH public key response differed by 1 byte to what I was expecting, from an info page. I was tempted to ...
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1answer
111 views

Is limiting access to a web script with .htaccess secure enough when that script can run arbitrary commands?

Okay, so I don't have much HTML experience, but I recently started working on a project with a group of people that involves regularly manipulating files in a web server. I would like to work on this ...
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2answers
265 views

Why does ssh `known_hosts` file need server name?

When I push/pull repos on GitHub over SSH, sometimes there will a message about unidentified server and asks if I want to trust and add it to known_hosts. Apparently this is because GitHub has ...
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2answers
149 views

Receiving sensitive data uploaded on a Web server, and remotely accessing it without exposing it to theft

Edit: I mostly used my university's guidelines on how to meet DPA standards and their own. I extrapolated a bit because encryption on a VM hosted by my uni that is already probably encrypted makes ...
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1answer
6k views

Fail2Ban does not ban failed root login attempt

I have a small server which only open ports are ssh, http and https. I have fail2ban installed and set up so that after 3 failed attempts someone gets blocked for 10 minutes (thats the dafault I ...
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2answers
183 views

How common is port-knocking? [closed]

Today I read about port-knocking for the first time. It has been a pretty known concept for more than ten years, but I don't know anybody who uses it for their servers. How common is the usage of ...
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1answer
784 views

SFTP between guest virtual machine and its host

The System I am using Windows 7 host with Cygwin and a virtual machine running Linux. The actual running guest is an Arch Linux ISO. The Objective I want to share files between the Cygwin host and ...
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4answers
1k views

Why secure encrypted data consistency by strong hashing?

Consider the SSH protocol: the SSH packet is like [data, SHA1(data)]. The packet is entirely encrypted by a block cipher. The question is, why do we need a strong hash to protect the packet ...
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1answer
160 views

Should I use the root account on my Digital Ocean server?

I have set up an SSH key with Digital Ocean that is automatically added to any servers I create. Is it okay to use this root account for SFTP and daily use or should I create another user account and ...
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7answers
497 views

Is it wrong to root login with SSH?

I've long been under the impression that with unix, you should never login as root. Now I've started using Virtual Private Servers over at DigitalOcean, and some advice is to use SSH keys to login as ...
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0answers
36 views

SSH web server good practises [duplicate]

Is it risky to open the SSH service on a web server (even with a strong password or with RSA keys) ? What are good practises to connect to a web server for maintenance ? Thank you !
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139 views

Do SSH private keys always contain enough information to derive a public key?

I am working on a persistence model for SSH Private keys. The technology used is Java. Since the persistence structure of the public and private keys is pretty similar and using some of the Java APIs ...
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141 views

How to transfer securely a file between servers?

Let's say I have two Linux servers. One containing a desktop app database (running on a local network) and a webserver. I want to automatically transfer each hour a database file (with a size of a ...
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1answer
685 views

TrustWave PCI Compliance - OpenSSH

First time 'asker' on here, but wanted to say thanks to how much I've used this site and reading answers to questions I've had! Anyway, lately I've been having issues with a customer of ours who's ...
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2answers
189 views

Is my ssh server safe because I use DenyHosts and don't allow root access?

I am by no means an expert in online security so I wanted to outline the steps I am taking to remain as safe as possible yet still make it as easy as possible to gain access to my system from anywhere ...
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2answers
224 views

Using given RSA private key without the associated public key

I'm currently following a small game to get more familar with linux and security and got the following task: The password for the next level is stored in /etc/bandit_pass/bandit14 and can only be ...
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4answers
367 views

How should I defend against zero-day attack on SSH?

Vulnerabilities are discovered everyday. The recent Heart bleed attack caught many people off guard. I was wondering if a serious flaw was to be discovered that allows unfettered access to SSH, how ...
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4answers
3k views

What are the chances to generate the same ssh key?

I could generate ssh keys on the client like (without password): ssh-keygen -b 8192 -t rsa -f /home/THEUSER/.ssh/id_rsa -P '' -v and copy the generated id_rsa.pub to the server: ssh-copy-id -i ...
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2answers
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Is it not safe to open MySQL's port to the internet?

The consensus on this Server Fault question seems to be that opening port 3306 for MySQL is more dangerous than using an SSH tunnel to access MySQL. I would think that with strong credentials you ...
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3answers
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Is it a bad idea to share the ssh host key in a diskless environment?

I am looking at this cluster of student work stations. They are diskless clients which boot from NFS. They also have sshd enabled. All of these machines share the same ssh host key (rsa,dsa,etc), ...
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4answers
2k views

Brute forcing ssh keys

My problem is a common one: I deleted my SSH key, and forgot to set rm to point to a .trash file. I have the public key, and I need to get in this server. I am not doing this on anyone else's server. ...
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1answer
968 views

find passphrase on encrypted ssh private key

I have an openssh encrypted private key. I don't remember the pass-phrase. I may be able to suggest words or patterns that may be in the phrase. I am looking for software that will help me recover ...
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2answers
2k views

How can I make a read-only filesystem read/write?

I recently hacked into my router which runs BusyBox v1.9.1. I want to edit some files in my web GUI interface which will allow me to get hidden options in it. I'm trying to edit a .js file and replace ...
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2answers
116 views

Disable all SSH security mechanisms for a private subnet

So I'm running a private subnet where there is no internet connectivity, I understand the grave danger of running an ssh server on the internet without security. In short I would like to be able to ...
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1answer
50 views

What are the security issues of a MITM on an ssh session with rsa keypair

If a user connects to an SSH server using an rsa private key, but does not confirm the server's fingerprint. What kind of information can a man in the middle attack get from the session?
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336 views

Should remote access (RDP/SSH) only be allowed for VPN clients? Or should RDP and SSH be opened the public?

I am about to push hard against the powers that be and strongly recommend that we shift our many (20+) consultants from direct public access to RDP & SSH to VPN clients (connecting to a ...
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1answer
165 views

Linux SSH and GPG

Can anyone please give me a quick crash course on SSH and GPG? SSH: What is the difference between public and private keys? Should I back up my ~/.ssh/ directory, what are the security implications ...
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2answers
709 views

Storing SSH private keys on an Android device

(I'm not sure if this better belongs on unix.se or android.se, but since it's primarily security-related, I'm asking it here) I use my Android device to access servers for quick on-the-go ...
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1answer
694 views

Open source solution to capture and decrypt SSH traffic (with private key)?

I am looking for a free open source solution that is able to capture and decrypt SSH traffic given the fact that I can provide the server's RSA private key (something like SSH CryptoAuditor). Please ...
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2answers
178 views

Should I use more than 2048 bits in my SSH-2 RAS Key?

I've been asked to generate a public key with PuTTY Key Generator. The default is 2048 bits, Should I add additional bits to the generated key? Or is it unnecessary?
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2answers
412 views

Given an IP address can you ssh into /tmp without password?

I'm a Software Engineer, but I have no experience in security, so i'm trying to learn by doing (woot Experiential learning!). I know that the permission settings on the tmp folder are very relaxed. ...
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2answers
254 views

Can a SSH server or client to initiate a unencrypted connection?

Several clarifying questions: Is it possible to disable the SSH encryption using options at the OpenSSH server/client or some appropriate hack? Is it possible to do this at the time of the ...
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248 views

Working from many places <-> being able to restrict SSH access to server to IP range

I administer a webserver, and while I'd like to restrict the SSH access to an IP range, I wouldn't be able to do so because a) I travel a lot and b) I don't have a static IP at my homeoffice. I've ...
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88 views

can ssh port forwarding be detected?

say there are three players: A, B, C where A is local machine, B is ssh server, C is the final destination. through ssh local port forwarding, A can connect to C via B. So then data will be ...
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68 views

what is a server fingerprint in ssh?

Is is the same as a public key in RSA, except they made it more suitable for self-signed hosts? What happens behind the scenes when our ssh client presents it to us?
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510 views

I want to roll my personal cloud hosted Password Manager using pass. How secure/insecure would this be?

I've come to the conclusion that I need to up my security. I currently have a dozen memorized passwords I use for every device and website. I'm against Keypass/Lastpass due to having to trust they ...