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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DSA, ECDSA and RSA

Conventional wisdom these days is that in the context of SSH keys, DSA is insecure and RSA is preferred (or that they are both fine, but RSA is more secure, depending on who you ask). As I understand ...
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SSH cache secrets

Why does SSH use public key crypto each time you connect to the server? RSA/DSA are computationally expensive, so why can't they just be used the first time to share a secret, and then in the future ...
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How should I tunnel arbitrary protocol traffic over HTTPS?

I'm posting this question from a moving train! (Ok, maybe that's not so impressive.) This train has an annoying WiFi - it's low-throughput, high-latency, tends to lose packets, and blocks most kinds ...
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SSH-Keygen Fingerprint providing Letters and Numbers Result [on hold]

I've been using SSH and public key crypto for a few months. I've run into a new problem with my install of the newest public beta of OS X, and can't find an answer online. When I run SSH-Keygen -lf ...
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Is using a public-key for logging in to SSH any better than saving a password?

Using a public/private key pair is fairly convenient for logging in to frequented hosts, but if I'm using a key pair with no password, is that any safer (or less safe) than a password? The security ...
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Managing SSH key access to AWS servers behind bastion

enter link description hereI currently have an AWS setup with 3 VPCs, one for the bastion, then a Dev and a Prod VPC, those last two only being SSH accessible via the bastion of course (layout from ...
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How do RSA fingerprints protect from MITM attacks?

I understand that RSA fingerprints are used to verify that you are really connecting directly to who you want to connect to, and not someone else posing as that site. Like when you do a git push, it ...
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length of ciphers versus length of key

ssh-keygen defaults to RSA (for SSH protocol 2) and a 2048 bit key. At this description of ssh The supported ciphers are: 3des-cbc, aes128-cbc, aes192-cbc, aes256-cbc, aes128-ctr, ...
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Best practice to guard against an app copying private ssh keys stored under ~/.ssh?

Given that any application running as the logged in user will have read access to that user's ~/.ssh folder, it seems trivial for the application to copy that user's private key and send it over the ...
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Managing multiple SSH private keys for a team

I have a medium-sized team (~10 people, but we expect to grow) that manages a set of EC2 servers on AWS (currently a few dozens, but this is also expected to grow). As EC2 requires you to have an ...
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What is the correct way to set up a VPN and then only allowing SSH from that VPN? [migrated]

What is the correct way to set up a VPN and then only allowing SSH from that VPN? I want to set this up to remove my SSH from the open internet and only allow access via a dedicated VPN connection, ...
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Can people know the server I'm connecting to despite being on SSH/HTTPS? [duplicate]

I understand that by connecting securely over SSH or HTTPS, the data that I transfer is cryptographically secure. However, can someone spying on my connection still determine the server I'm sending it ...
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Invalid users trying to log in to my server

I'm seeing a lot of log entries that appear to be failed login attempts from unknown IP addresses. I am using private and public keys to log in with SSH but I have noticed that even with private ...
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1answer
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Why does the server ssh public key not look like the key in client known hosts?

From my naive understanding of ssh, the server shares its public key ( /etc/shh/ssh_host_rsa_key.pub ) with the client, who then adds it to the list of known hosts ( /user/.ssh/known_hosts ). So, I ...
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Is it possible for an SSH MITM to attack only if the key isn't in the known_hosts?

I was trying to connect a server using a different port when the network seemed too slow. It gives an ECDSA key, while the previous key in the known_hosts is RSA. I refused to continue the connection ...
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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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Managing passwordless SSH authentication from servers to server

I have a bunch of servers that need to transmit data to one server using SCP. What is the best practice for using SSH key-based authentication? Option 1: Create a unique private key for each host and ...
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How to set up OpenSSH to use x509 PKI for authentication?

I do not mean simply putting the public RSA key of a x.509 certificate into ~/.ssh/authorized_keys - I'm looking for a way to set up a ssh such that x.509 certificates signed by a pre-defined CA will ...
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1answer
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PPP over SSH - is this correct?

I see a lot of talk online about whipping up a VPN connection using PPP over SSH. This term confuses me, as SSH is an app tier protocol and PPP operates on the data-link layer. So, my question is: ...
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Repeated security questions after remote key has changed

I reinstalled one of my machines and gave it new ssh keys, which should yield warnings when I connect to it from a machine I have connected from earlier. First I get the big warning that the remote ...
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1answer
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Protecting SSH service with many inexperienced users

One of the universities I know has a rather unique password policy. They issue shell accounts to all computing students with strong passwords that are unchangeable. It is done via the passwd -n flag ...
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Digital Ocean “Droplet” allgedly compromised for trivial, unpublicized website. Should I be worried abouty my own machine?

I got a message from D.O. about my Droplet saying they shut it down because there was a lot of outgoing traffic that looked like an attack. The site I had on that server was not very known at all. ...
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My friend revealed both private and public keys for his server. How serious is this?

A friend of mine managed to expose both id_rsa and id_rsa.pub file from his server via apache. I mentioned to him that this is serious security issue but he brushed this off like it was no big deal. ...
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Does SSH password authentication provide the server with the password?

If an attacker takes control of a server and a user tries to SSH into it using password authentication, can the attacker get the password? I was under the impression that there was an algorithm in ...
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Private VPN server in public cloud

I need to encrypt all my traffic, because I often work in unsecure network environments. My questions is this: if I buy my server from VPS providers (amazon ec2, digitalocean, etc) - how secure ...
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Can you use ssh for secure inter app communication on the same device?

I use ssh to get an encrypted connection between servers and local machines all the time. It's fast, it's secure, and there's a way to do it in nearly every system programming language that I've used ...
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How secure is socks5 proxy over ssh?

At work we are all using Windows 7+, with full administrative privileges. Each PC has a dedicated IP and a proxy is used. It is set as a HTTP proxy and the option to use this for all types of ...
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SSH key auth, but still need password for sudo?

SSH with public-private key authentication comes enabled by default with most Linux distributions. This is great because when I create accounts for remote users I don't have to email them sensitive ...
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Logging all traffic crossing SSH proxy

Is there a way to log SSH sessions proxied through a machine (User-> SSH Proxy -> Server (with SSH)) without modifying the SSH daemon on the proxy? I need to log all the commands as well as responses ...
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Management of server keys

I plan to put an SSH server on micro-controller devices. There shall be many devices distributed in a wide range. The identity of the server is checked with the server key. The server needs to store ...
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Detect SSH InBound / Oubound Connections

I'm noodling with the idea of managing SSH connections on Linux server using a program (not sure what it will be written in yet) that monitors inbound and outbound connections. Is there a way to ...
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Adding a binary to the firmware of a routing device [closed]

I've been playing around with a router d-link dwr-921 and found some vulnerabilities in the web interface. I still haven't managed to get shell access and now I'm thinking about modifying the firmware ...
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Are OpenSSH vs OpenSSL public key format names mismatched?

I generated a key pair vis OpenSSH and later wanted to generate PEM encoded public key. I noticed that generated public key differs when generated by OpenSSH vs OpenSSL when using same format name ...
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Is it possible having only public key from SSH keypair to see if private key is password protected?

As a person responsible for security I wonder on this subject. To provide best security I don't want to accept/deploy public keys for users if private key is not password protected. However there ...
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SFTP on Windows - is it likely to be disabled?

I'm a software engineer and I'm maintaining a product that allows a user to run commands and scripts on Linux servers via an SSH connection. We now need to extend this functionality onto Windows. We ...
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Can an attacker “simulate” a private IP address?

I have a SSH server with a rule that does not allow password connections outside the local network. So people already on the local network, either physically or via VPN, are allowed to connect with ...
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Converting keys between openssl and openssh

If I use the following openssl req -x509 -days 365 -newkey rsa:2048 -keyout private.pem -out public.pem -nodes I get private.pem and public.pem If I use ssh-keygen -t rsa -f rsa I get rsa and ...
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Public/private key auth and VPN

If a server uses public/private key authentication to access SSH, will there be any advantage of restricting the access of SSH over VPN? This link describes both approaches to solve brute force ...
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Security of nested ssh

First of all, by nested ssh, I mean the following way of using ssh: ssh usera@Bob 'ssh usera@C' suppose A wants to login on server C, but for some reason C is not directly available to A (e.g. C's ...
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Server compromised with magento vulnerability, possible rootkit

I am experiencing a security issue with one server that it happens that I manage. I will try to cite all relevant facts as briefly as possible. I am asking for any additional information and course of ...
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Analyzing log files for forensics homework?

Suppose two users have done a murder at 6pm at Dunkin Donuts, I have got the hard disks on site, disk1 and disk2. How do I identify the time and order of each user's activities on the hard disks? ...
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Security Concerns with X11 Forwarding

What are some of the security concerns and reasons either for or against allowing X11 Forwarding. I have generally taken an approach of not allowing it under the blanket guise of security. Recently, ...
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Will two virtual machines running on the same physical host machine get the same value from /dev/random?

Will two virtual machines running on the same physical host machine get the same value from /dev/random if read over the same time period? Say that Virtual-machine-1 wants to generate its ssh host ...
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Does enabling VPN on our router increase the risk of our network being exposed to the outside network? [closed]

We are thinking about using VPN to connect our remote office and the main office and also support developers working from home. To do this, we are planning to purchase 2 CISCO (or similar) routers to ...
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Convert RSA openSSH key/putty key to gpg key [closed]

Scenario Two work sites, site 1 and site 2. Two Linux servers, server A and server B. Server A is reachable from both sites, while server B is reachable from site 1 only. Two Windows workstations, ...
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What is the difference between SSL vs SSH? Which is more secure?

What is the difference between SSH and SSL? Which one is more secure, if you can compare them together? Which has more potential vulnerabilities?
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Risks of having SSH private key stolen

I'm afraid this is quite a common question, but searching several times through the questions did not prove useful, and I'm really eager of knowledge here :D I understand that keeping SSH private key ...
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Sharing RSA keys between PGP and SSH protocols: Does this pose a security risk?

If I generate a PGP subkey that only has the authentication capablity and use this to generate an SSH keypair to authenticate Git for example, does this pose a security threat? When I do, should I ...
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Metasploit SSH Error: could not settle on kex algorithm

I am running a trial of Cobalt Strike which runs over the Metasploit Framework. I am trying to perform an SSH related attack on my laptop, and I get the error in the title for all SSH related attacks. ...
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Is it considered worth it to replace OpenSSH's moduli file?

Consequences of tampered /etc/ssh/moduli describes a possible risk if the moduli file for an OpenSSH server has been tampered with. Taking the logic a step further, is there any concern with the ...