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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.

16
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1answer
1k 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 ...
0
votes
1answer
58 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 ...
3
votes
1answer
79 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-...
1
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0answers
53 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 ...
1
vote
1answer
44 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 ...
3
votes
1answer
88 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 ...
-7
votes
1answer
426 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 ...
5
votes
3answers
183 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 ...
0
votes
1answer
82 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-...
1
vote
1answer
472 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 ...
0
votes
1answer
73 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'...
1
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0answers
192 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 ...
0
votes
1answer
122 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 ...
0
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1answer
1k 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 ...
0
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0answers
260 views

Openssl SSL_CTX_set_cipher_list() in cross-platform C application

Situation I am developing a cross-platform C application which uses OpenSSL. I would like to release it for at least the following operating systems: Windows 7+ MacOS High Sierra Debian 8+ Ubuntu ...
1
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1answer
86 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 ...
2
votes
1answer
400 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 ...
0
votes
1answer
102 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, ...
3
votes
1answer
1k 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
votes
1answer
136 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 ...
2
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1answer
44 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. ...
0
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1answer
61 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 ...
1
vote
2answers
127 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 ...
1
vote
2answers
776 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 ...
1
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0answers
91 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 ...
1
vote
1answer
500 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 ...
1
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0answers
1k views

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 (...
6
votes
3answers
4k 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 ...
0
votes
1answer
613 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 ...
1
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1answer
756 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=...
1
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3answers
232 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, ...
1
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1answer
2k 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 -...
1
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2answers
2k 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....
1
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2answers
308 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....
0
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2answers
93 views

Given the following yaSSL ciphers, how do I know what's being used?

Scope: I am considerable new on cryptography and only know some basic fundamentals of it. Looking at yaSSL ciphers I am trying to, as an exercise, to figure out which ones are still safe to use by ...
0
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1answer
73 views

Changing cipher list of a ctx object after connection establishment

Does changing the cipher list for a CTX object (using SSL_CTX_set_cipher_list), have any effect on the already established connections (connections that had used that very CTX object)?
1
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1answer
471 views

How to make TLS_RSA_WITH_3DES_EDE_CBC_SHA strong

First off I have NO idea what ciphers are and my knowledge is very basic in security! With that said, from this tutorial I have established a secure SSL site and I have a ran a test on my domain and ...
1
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1answer
2k views

What is the difference between CBC and CBC3 cipher suites? [duplicate]

Consider below cipher suite TLS v1.0 TLS_RSA_WITH_DES_CBC_SHA **DES-CBC-SHA** TLS_RSA_WITH_3DES_EDE_CBC_SHA **DES-CBC3-SHA** Wwhat is the meaning of CBC and CBC3, and what ...
-1
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1answer
245 views

what is wrong with openssl ciphers?

I used openssl recently and noticed that in the cipher list there is AES (what else ) and then I saw many rarely used ciphers like camellia and seed, then I saw stuff like rc4, rc2 ... Why are ...
5
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1answer
4k views

Server negotiated HTTP/2 with blacklisted suite

I understand there are quite a few posts regarding my error message, and I have looked at them with no luck to resolving my own issue. Essentially, certain web browsers are unable to load my site ...
1
vote
1answer
64 views

Does Firefox implements SCSV?

I need to know if Mozilla Firfox implements the SCSV which adds a specific ciphersuite in case if the client initial hello message is resent (either due to MITM or due to network erro). I opened ...
5
votes
3answers
365 views

TLS Cipher Suites for MTA

When configuring a mailgateway’s TLS Settings, should one stick to the same rules for Cipher Suites as in running a HTTPS Service (prefer EDCHE/DHE, disable SSLv3, not use stuff like RC4, etc.) or ...
2
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0answers
2k views

OpenVPN cipher mode of operation: CFB vs CFB1 vs CFB8

I'm trying to understand the possible settings for the cipher in OpenVPN and somehow rank them security wise. Right now I'm stuck at differentiating the modes of operation CFB, CFB1 and CFB8. How do ...
3
votes
1answer
255 views

Guidelines for TLS cipher suites?

Other than OWASP, are there any other guidelines for recommended TLS/SSL versions as well as their specific cipher suites?
3
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1answer
592 views

What cipher suites do Mail Clients (Thunderbird, Outlook, …) support?

This question is related to this Super User question. What cipher suites do Mail Clients (Thunderbird, Outlook, ...) support? I know and appreciate the service of SSLLabs where I can see the ...
2
votes
1answer
6k views

Why does Chrome warn about “Obsolete Connection Settings” for key exchange?

What do I have to change so Google Chrome won't say that I am using an obsolete key exchange? Obsolete Connection Settings The connection to this site uses a strong protocol (TLS 1.2), an ...
2
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1answer
556 views

weak cipher suites Qualys SSL Labs test

I was wondering when running tests using let's Qualys SSL Labs against for example say a cloud based web service and as a result it says that the site is using weak ciphers does that mean that the ...
0
votes
2answers
836 views

Why are larger block sizes more desirable?

I've read three different exceperts from three different information security books, to summarize, this is what they say: "Block size impacts security, complexity, and performance. A larger block ...
2
votes
1answer
1k views

Which cipher suites are proposed by client and which one chosen by server?

I've sniffed several TLS/SSL communication with Wireshark, and I want to find out which cipher suites are proposed by client and which one chosen by server. How do I do that? Here you have some of ...
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2answers
2k views

Difference between two TLS cipher suites

I want to know the difference between these two cipher suites: TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 TLS_RSA_WITH_AES_128_GCM_SHA256 My questions are: In the (2) there is no key exchange algorithm (...