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| ssh 2014-10-01 | ssh 2023-06-05 (current) | ||
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| ====== Understanding SSH ====== | ====== Understanding SSH ====== | ||
| SSH is a cryptographically protected remote login protocol that replaces insecure telnet and rlogin protocols. It provides strong protection against password sniffing and third party session monitoring, better protecting your authentication credentials | SSH is a cryptographically protected remote login protocol that replaces insecure telnet and rlogin protocols. It provides strong protection against password sniffing and third party session monitoring, better protecting your authentication credentials | ||
| - | and privacy. In addition, SSH offers additional authentication methods that are considered more secure than passwords, such as public key authentication and extensive | + | and privacy. In addition, %%SSH%% offers additional authentication methods that are considered more secure than passwords, such as [[public_key|public key authentication]] and extensive |
| protection against spoofing. | protection against spoofing. | ||
| - | ~~TOC~~ | + | The %%SSH%% employs a public key cryptography that uses [[ssh_keys|two keys pairs, for host and user]]. |
| - | ===== Authentication in SSH ===== | + | ===== [[authentication]] Authentication in SSH ===== |
| SSH servers offer the client a selection of authentication | SSH servers offer the client a selection of authentication | ||
| methods. The server advertises what it supports, and the client | methods. The server advertises what it supports, and the client | ||
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| the option to choose which methods can be used. In WinSCP, you can configure this on //[[ui_login_authentication|SSH > Authentication page]]// of Advanced Site Settings dialog. | the option to choose which methods can be used. In WinSCP, you can configure this on //[[ui_login_authentication|SSH > Authentication page]]// of Advanced Site Settings dialog. | ||
| - | The actual order of authentication methods is as follows: [[ui_login_authentication#gssapi|GSSAPI]] (SSH-2 only), [[public key]] (using [[ui_pageant|Pageant]]), public key (using [[ui_login_authentication|configured file]]), keyboard-interactive (SSH-2 only), TIS or Cryptocard (SSH-1 only), password. | + | The actual order of authentication methods is as follows: [[ui_login_authentication#gssapi|GSSAPI]], [[public key]] (using [[ui_pageant|Pageant]]), public key (using [[ui_login_authentication|configured file]]), keyboard-interactive, password. |
| - | ===== Verifying the Host Key ===== | + | ===== [[verifying_host_key]] Verifying the Host Key ===== |
| - | To prevent [[wp>Man-in-the-middle_attack|man-in-the-middle attacks]], each SSH server has a unique identifying code, called a host key. These keys prevent a server from forging another server's key. If you connect to a server for the first time or if the server presets a different key then previously, WinSCP will prompt you to [[ssh_verifying_the_host_key|verify the key]]. | + | To prevent [[wp>Man-in-the-middle_attack|man-in-the-middle attacks]], each SSH server has a unique identifying code, called a host key. These keys prevent a server from forging another server's key. If you connect to a server for the first time or if the server presets a different key than previously, WinSCP will prompt you to [[ssh_verifying_the_host_key|verify the key]]. |
| ===== Encryption in SSH ===== | ===== Encryption in SSH ===== | ||
| - | SSH clients and servers can use a number of encryption methods. In the older SSH-1 protocol, 3DES and DES are typically used. | + | SSH clients and servers can use a number of encryption methods. |
| - | SSH-2 adds support for additional encryption methods including AES and | + | Most widely used encryption methods in SSH are AES and |
| - | Blowfish. By default, Blowfish is used if supported by the server. While AES is | + | Blowfish. By default, %%AES%% is used if supported by the server. While %%AES%% is |
| - | considered to be highly secure, AES encryption requires substantial processor overhead. Blowfish is also considered | + | considered to be highly secure, %%AES%% encryption requires substantial processor overhead. Blowfish is also considered |
| secure, but with less computational overhead, it's also theoretically | secure, but with less computational overhead, it's also theoretically | ||
| easier to perform a brute-force attack. Depending on your security and | easier to perform a brute-force attack. Depending on your security and | ||
| performance requirements, you may wish to configure WinSCP to prefer | performance requirements, you may wish to configure WinSCP to prefer | ||
| - | the AES algorithm. 3DES and DES are used with SSH-1 servers. DES | + | the %%Blowfish%% algorithm. %%3DES%% and %%DES%% are used with %%SSH-1%% servers. %%DES%% |
| is widely regarded as insecure, as the resources to perform an | is widely regarded as insecure, as the resources to perform an | ||
| exhaustive brute-force attack have been well within the realm of | exhaustive brute-force attack have been well within the realm of | ||
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| ===== SSH Protocols ===== | ===== SSH Protocols ===== | ||
| - | Two major versions of the SSH protocol are in widespread use. | + | Two major versions of the SSH protocol exist, SSH-2 and SSH-1. Most %%SSH%% servers nowadays allow modern and secure %%SSH-2%% only, which is also WinSCP's default. |
| - | The SSH-1 protocol is an older version that's still | + | |
| - | widely supported despite its age and some technical issues. The SSH-2 | + | |
| - | protocol has become the de-facto installation standard, though some systems only support SSH-1. In addition, many sites that use SSH-2 disable the SSH-1 protocol | + | |
| - | for security reasons. | + | |
| - | WinSCP's default setting is to prefer SSH-2 and negotiate | + | ===== [[compression]] Compression ===== |
| - | down to SSH-1 if SSH-2 is not available. If the majority of systems you | + | |
| - | connect to are using SSH-2, you may wish to change this setting in the | + | |
| - | [[ui_login_ssh|SSH preferences]]. | + | |
| - | + | ||
| - | ===== Compression ===== | + | |
| SSH supports data stream compression between the client | SSH supports data stream compression between the client | ||
| and the server. On slow links, this may increase throughput, while in faster connections the added CPU overhead may actually result in | and the server. On slow links, this may increase throughput, while in faster connections the added CPU overhead may actually result in | ||
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| attacks more difficult and by providing less data for | attacks more difficult and by providing less data for | ||
| cryptanalysis. | cryptanalysis. | ||
| + | |||
| + | ===== Supported Algorithms ===== | ||
| + | |||
| + | See list of [[ssh_algorithms|supported SSH algorithms]]. | ||