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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.

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P-384 vs. SHA384

Forgive my inexperience with encryption, I've been researching this for the better part of the morning and still cannot find a smoking gun answer. A vendor is requesting that we verify a website we ...
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4 answers
130 views

Which cipher is more secure TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA or TLS_RSA_WITH_AES_256_GCM_SHA384?

TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA supports forward secrecy but it doesn't use GCM mode and use SHA1 TLS_RSA_WITH_AES_256_GCM_SHA384 uses GCM mode and SHA2 but it doesn't support forward secrecy. ...
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2 votes
2 answers
62 views

Java support for TLS_DHE_RSA_WITH_AES_128_CCM

My test tool uses java and I need it to use TLS_DHE_RSA_WITH_AES_128_CCM. Does standard java (Oracle) support CCM cipher suites? I am seeing oracle links mentioning CCM but am not able to make it work....
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3 votes
2 answers
467 views

Cipher suite choice on macOS on Apple Silicon

I have a postfix mail server that accepts these cipher suites: tls_high_cipherlist=ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256: ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384: ...
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1 answer
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How does TLS use hashing from the negotiated cipher suite

I am trying to understand why TLS only uses hashing algorithm like SHA-384 instead of using an HMAC instance like HMAC-SHA-384. If I understand correctly, this cipher suite (...
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1 vote
0 answers
64 views

Should I manually select protocol and cipher?

I'm writing Java code for a decentralized network. (Proof of concept code here.) Each node generates its own self-signed certificate, to be used both server-side and client-side in every connection. ...
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2 votes
1 answer
562 views

How are key exchange and signature algorithms negotiated in TLS 1.3

In TLS 1.2, the cipher suite lists the algorithms for everything (key exchange, signature, cipher/MAC). So by choosing a suite, all the algorithms will have been negotiated. And I can see them from ...
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2 votes
4 answers
379 views

SSH Server Configuration Best Practices?

I have been tasked with reviewing the settings of an SSH server, I'm currently trying to figure out what are the best practices, and I'm having a bit of trouble finding a good answer. I keep finding a ...
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0 answers
445 views

Are Brave Browsers Sync encryption parameters secure enough?

I am considering switching over to Brave and maybe also use it's sync feature for settings, and maybe even passwords if it's good enough. I do use a password generator but out of laziness I happen to ...
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1 vote
1 answer
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Should hashing algorithm used for X.509 certificate's signing match the algorithm used in the communication

I've seen this but the related answers don't answer my question. For TLS 1.2 is the hashing algorithm specified in an X.509 certificate's cipher suite used for the signature inside the certificate or ...
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3 votes
1 answer
192 views

Why can SSH negotiatie two different encryption and authentication algorithms?

I recently found out, that according to the RFC, SSH can negotiate two different cipher (and MAC) algorithms for server-to-client-encryption and for client-to-server-encryption (check section 7.1. for ...
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1 answer
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Is it possible to view the cipher suites offered on my behalf by a MITM proxy?

I'm trying to discover what cipher suites are being offered by my corporate proxy. It's set up as a man in the middle so my "secure" connections are to it, and it attempts to create a ...
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0 votes
1 answer
165 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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1 vote
2 answers
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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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2 answers
761 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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1 answer
173 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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2 votes
1 answer
162 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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0 votes
2 answers
776 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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1 vote
0 answers
6k 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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0 answers
111 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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1 vote
1 answer
287 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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1 vote
1 answer
236 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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1 answer
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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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  • 137
1 vote
0 answers
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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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3 votes
3 answers
277 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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0 answers
87 views

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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2 votes
0 answers
89 views

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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2 votes
1 answer
164 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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19 votes
1 answer
13k 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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0 votes
1 answer
218 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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3 votes
1 answer
288 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-ecPublicKey ...
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1 vote
0 answers
197 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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1 vote
1 answer
335 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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4 votes
1 answer
191 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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-6 votes
1 answer
4k 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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8 votes
3 answers
6k 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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  • 513
0 votes
1 answer
847 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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2 votes
1 answer
5k 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 ...
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3 votes
1 answer
1k 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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1 vote
0 answers
2k 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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0 votes
1 answer
309 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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1 vote
1 answer
3k 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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1 vote
1 answer
344 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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2 votes
1 answer
908 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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0 votes
1 answer
218 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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3 votes
1 answer
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 ...
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2 votes
1 answer
389 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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2 votes
1 answer
86 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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0 votes
1 answer
117 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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1 vote
2 answers
239 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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