Questions tagged [cipher-selection]

For questions about the step of the SSL/TLS handshake where the cipher is negotiated between the client and the server. This tag could also be used for questions about which ciphers to support in your application / configuration.

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40 views

Nginx with only TLS1.3 cipher suites [migrated]

I am trying to configure Nginx to use only TLS1.3 with 2 ciphers: TLS-AES-256-GCM-SHA384:TLS-AES-128-GCM-SHA256. So, I tried this configuration: ssl_protocols TLSv1.3; ssl_ciphers TLS-AES-256-GCM-...
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1answer
38 views

Find out the least insecure mutual cipher algorithm

I have set the cipher algorithms for ssh on my server to just chacha20-poly1305@openssh.com, aes256-gcm@openssh.com and aes128-gcm@openssh.com Now my IntelliJ fails with this error: failed: unable ...
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2answers
89 views

OpenSSH: Meaning of cipher with email address @openssh.com

When using OpenSSH server (sshd) we specify allowed ciphers, host key algorithms and MACs. Some of those ciphers have an email address appended, for example aes256-gcm@openssh.com as opposed to aes256-...
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2answers
107 views

When connecting via SSH, does the Diffie-Hellman key exchange take place over an unencrypted TCP session or does encryption occur before the exchange?

I'm a cybersecurity student and I'm eager to understand the basic processes of an SSH session. I wrote down the stages to the best of my ability but need help understanding what happens right after ...
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1answer
48 views

what is the link between server certificate and cipher list advertised by server for nmap command?

Nmap out put for google.com. ssl-enum-ciphers. TLSv1.2: ciphers: TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA (ecdh_x25519) - A. TLS_ECDHE_ECDSA_WITH_AES_128_GCM_SHA256 (ecdh_x25519) - A. ...
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1answer
97 views

What is the purpose of TLS cipher suites pairing? Why are they paired the way they are?

Why are there predefined sets of cipher suites. Why is creating your own cipher suites not recommended.
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2answers
95 views

Remove less secure ciphers from WHM by decrpyting different convoluted references to the same ciphers

I have previously removed less secure ciphers from WHM (Web Host Manager) however it has been a while and I want to learn how to fish, not be handed a fish. The trouble seems to stem from the fact ...
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0answers
128 views

TLS handshake failure (40) solved by removing intermediate certificate from server?

I'd like to better understand my workaround, and confirm that it's secure. Problem I have a crt file containing a root and intermediate certificate installed on my server (I have limited access to ...
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39 views

Does the entire certificate chain need to be signed with the agreed upon cipher under TLS? [duplicate]

Security Newbie, I'm using OpenSSL for my client, and noticed that when testing it against Bad ssl's sha1-intermediate test, it accepts it although the agreed upon cipher is ...
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1answer
88 views

Force specific encryption cipher for S/MIME mails

I have a number of contacts who can only decrypt 3DES, when it comes to S/MIME encrypted mails. I'm aware that this is by far not ideal, but better than no encryption at all. My problem is, that I ...
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1answer
54 views

How do I verify the supported ciphersuites of a TLS server that only accepts POST requests?

I'm currently trying to get a bidirectional TLS 1.2 connection working between 2 local Karaf-based XMLRPC servers that by design only accept POST requests. The environment is Windows 10 and both ...
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1answer
77 views

Why are the following two sets of ciphers “different”?

openssl ciphers -v 'ECDH+AESGCM:DH+AESCGM' gives: ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH Au=RSA Enc=AESGCM(256) Mac=AEAD ECDHE-ECDSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH Au=ECDSA Enc=...
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0answers
159 views

Openssl using the cipher parameter result in handhsake failure

When i use Openssl to connect to facebook.com I see 'ECDHE-ECDSA-AES128-GCM-SHA256' ciphersuite used. openssl s_client -connect www.facebook.com:443 SSL handshake has read 3280 bytes and written 373 ...
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3answers
208 views

Ensuring all network services on a device use strong TLS cipher suites

(This is hypothetical, but based on a real-life problem I've had) Context: I am developing an (embedded) device which includes a few exposed network services. I'm responsible for security, not ...
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Can someone explain the significance of Certificate Signature algorithm in the selection of Cipher suite in a TLS communication? [duplicate]

Can someone explain the significance of Certificate Signature algorithm in the selection of Cipher suite in a TLS communication?
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0answers
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Best luks setup disk [duplicate]

I want to encrypt my disk but I want to know what is the best configuration, I currently use ths: cryptsetup -v --cipher serpent-xts-plain64 --key-size 512 --key-file=- --hash whirlpool --iter-time ...
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1answer
85 views

IPsec installed algorithms

What happens if a laptop and a server don't have a encryption algorithm in common? Does IPSec abort the connection or does it always have default algorithms?
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1answer
6k views

How do I know which cipher suites can be disabled?

I have just performed a test on my personal webiste via SSLlabs.com and I'm apparently supporting some weaker ciphers. I've managed to improve several settings (like CAA), but I'm getting stuck at the ...
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1answer
77 views

Determine if cipher suite is weak [closed]

I'm wondering if there is a way I can determine if a cipher suite is weak using python code. For example given this cipher suite as input: TLS_RSA_WITH_AES_256_CBC_SHA I would want my code to return ...
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1answer
146 views

How to filter ciphers based on ssl certificate?

I have many ssl certificates. On one of the certificates I run the command openssl x509 -in cert.pem -text -noout it shows: Signature Algorithm: ecdsa-with-SHA256 Public Key Algorithm: id-...
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101 views

Who is responsible for Cipher selection and SSL handshake - Akamai, Load balancer, Publisher dispatcher, publisher

We have a AEM (Adobe experience manager) 6.2 application. I recently been advised to exclude/remove the weak ciphers for strict security policies. But I am not sure where shall I do the configuration ...
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1answer
120 views

OpenSSL Padding Oracle. Specific Ciphers on apache2 seems a little limited

I've seen a lot of articles giving the official explanation on how to prevent OpenSSL Padding Oracles, Usually all of them state that its CBC cipher suites that leave you vulnerable. The following ...
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1answer
142 views

What means that the same ciphersuite is both enabled and disabled in Java JSSE?

I am looking into documentation for JSSE ciphersuites in Java. https://docs.oracle.com/en/java/javase/11/security/oracle-providers.html#GUID-7093246A-31A3-4304-AC5F-5FB6400405E2 ...
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1answer
2k views

How to disable obsolete/insecure TLS_RSA ciphers to harden Chrome? [closed]

Multiple vulnerabilities have basically obsoleted TLS_RSA, CBC and QUIC implementations. February 9, 2019: "Seven researchers from all over the world found --yet again-- another way to break RSA ...
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3answers
936 views

What are the 'P' values in some cipher string?

Most of the cipher strings I see are in the format: TLS_DHE_RSA_WITH_AES_256_CBC_SHA256 TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384 TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256 ...
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1answer
397 views

Why are ciphers using DSS being offered when using DH+AES:!DSS?

When I run the following command on Windows 10 with OpenSSL 1.0.2p installed I receive a curious result back (Formatted for readability): openssl ciphers "DH+AES:!DSS:!aDSS:!aNULL" DH-DSS-AES256-GCM-...
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1answer
2k views

What are the best ciphers in terms of performance for SSH tunnel?

From a security standpoint, there are few good cipher options to use with SSH, such as ChaCha20, AES 128/256 GCM/CTR. As I understand (please correct me if I wrong), all of these offer pretty strong ...
2
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1answer
369 views

Is `tls_preempt_cipherlist = yes` in postfix a good idea nowadays?

Postfix' own documentation says it may cause issues, but only mentions "Windows 2003 Microsoft Exchange clients". Everything else I've found (first was CheckTLS, as far as I've been able to find, that'...
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786 views

TLS1.2, weak cypher suites and PCI DSS V3.2.1 compliance

Are below cypher suites, which are part of TLSv1.2: TLS_RSA_WITH_AES_128_CBC_SHA TLS_RSA_WITH_AES_128_CBC_SHA256 TLS_RSA_WITH_AES_128_GCM_SHA256 TLS_RSA_WITH_AES_256_CBC_SHA ...
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1answer
204 views

Understanding Cipher suite prefixes

I have been lately reading cipher suites and how it works. I figured how it works in the web servers and there is a doubt regarding the prefixes used in the order. How are RC4-SHA and RC4+SHA ...
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1answer
2k views

Understanding SSL Cipher suite in Apache

On reading the documentation Apache documentation. A cipher suite example has been given : RC4-SHA:AES128-SHA:HIGH:MEDIUM:!aNULL:!MD5 I have understood the explanation given by them. My question is ...
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1answer
205 views

Basic TLS questions: Implementing a specific TLS version and cipher

I've worked with TLS certs before, but only on a basic level. I'm trying to understand some specific recommendations for implementing TLS (quoted below). (For context, my goal is to secure HTTPS ...
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1answer
650 views

How does a client (like SSLLabs) know all the cipher suites a server supports if the server doesn’t send its list of supported cipher suites?

I was looking at the TLS handshake and I noticed that the client will send its list of supported cipher suites and the server will select a cipher suite. The server never sends its list of supported ...
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1answer
128 views

What cipher mode is usually used for network traffic encryption?

I'm currently teaching myself about cryptography with the intentions of learning more about cryptanalysis. As of now I'm learning about cipher modes! I understand that I should be looking into CBC, ...
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1answer
2k views

Clarifications regarding ciphers and Nmap scan

I'm running the below Nmap command to test the strength of the cipher suites I have used in my host nmap -sV --script ssl-enum-ciphers -p 443 <host> The Nmap doc says that Each ciphersuite is ...
2
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1answer
262 views

Is the server certificate taken into account during the cipher suite negotation phase?

I've a tomcat server with RSA certificate and connector X with a following suite: TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 My openssl client has the same suite: TLS_ECDHE_ECDSA_WITH_AES_128_CBC_SHA256 ...
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1answer
46 views

Clarification on Cipher Suite definition in Wikipedia

Can someone clarify me the difference (or similarity) between data and message described under Cipher Suite in Wikipedia The key exchange algorithm is used to exchange a key between two devices. ...
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1answer
69 views

Question on DH key exchange

The server is configured to support the cipher suite TLS_DHE_RSA_WITH_AES_128_CBC_SHA and validate the client's certificate. My understanding is that the server uses DH for key exchange which does ...
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2answers
175 views

What makes an SSL session pick one cipher over another?

I am curious as to what causes the SSL session to choose one cipher over another. I am a total novice with this, so most answers out there already are way over my head. Example: I need to connect to ...
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2answers
1k views

Why does tls_version “TLS 1.2” from howsmyssl rate “Probably Okay” in Chrome on Windows 10 but “Bad” in IE11 on Windows 7?

I'm implementing an API endpoint based on howsmyssl to check the TLS version of clients then notify those clients about whether or not they passed the test. However, several clients have reported ...
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0answers
152 views

Browsers not showing the protocol, key exchange and cipher information for my site using proper signed certificate for https [closed]

Browsers not showing the protocol, key exchange and cipher information for my site using proper signed certificate for https, but the debug from a java client accessing the same site shows following ...
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1answer
814 views

What are the benefits and disadvantage of disabling <TLS1.2 client side (in browser)?

We are considering disabling TLS1.0 and TLS1.1 in the policies for a browser used organization-wide. We already have a primary browser, where >=TLS1.0 is enabled (i.e. SSLv3 is disabled). We do not ...
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0answers
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SSL/TLS cipher suites order for Windows 2016 hosted https sites

We are SaaS & IaaS provider that predominantly use Windows 2012 (R2) for hosting. We have started evaluating Windows 2016 OS and noticed our sites are no longer accessible via Chrome / Firefox (...
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5answers
13k views

How to disable CBC-mode ciphers

Is there a simple blacklist-style way of disabling CBC mode cipher suites in apps that use an openssl cipher suite list? I'm hoping for something in the style of !RC4, however, !CBC has no effect, and ...
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1answer
795 views

Can key cipher and TLS cipher differ in OpenVPN?

I know how to configure OpenVPN and that there are control and data channels. But I did not yet find a nice overview of the crypto processes and especially how keys and certificates are really used in ...
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1answer
1k views

openssl PSK cipher support

openssl version on ubuntu machine is $ openssl version OpenSSL 1.0.2g 1 Mar 2016 Following is openssl PSK cipher list :- $ openssl ciphers -v 'PSK' PSK-AES256-CBC-SHA SSLv3 Kx=PSK Au=...
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3answers
356 views

Removing weak cipher support from TLS

We've run an audit on our public servers with SSL and had a few warnings for weak ciphers and potential SWEET32 vulnerabilities. It's our intention to remove every cipher that's secured with 3DES, ...
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1answer
3k views

selft signed certificate for AES128-GCM-SHA256 cipher

To generate self signed certificate for AES128-SHA256 cipher using openssl, following commands are used. AES128-SHA256 cipher commands :- openssl genrsa -aes128 -out 1.key 2048 openssl req -...
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2answers
3k views

SSL / TLS Ciphersuites [closed]

There's a large list of ciphersuites inside SSL / TLS. It seems like that these ciphersuites can be categorized in terms of their underlying mechanism with following categories: RSA Key Exchange (e.g....
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2answers
420 views

What would be a better encryption algorithm then RSA_DES_EDE3_CBC?

First off, please let me explain why I'm asking this at all: The default implementation of EnvelopedCms is using AlgorithmIdentifier which by itself will use RSA_DES_EDE3_CBC or OID 1.2.840.113549.3....