Questions tagged [tls]

SSL (Secure Sockets Layer) and its successor TLS (Transport Layer Security) are protocols which provide communication security (privacy and integrity) for a bidirectional data channel.

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25 views

HkdfLabel in TLS 1.3 [migrated]

In rfc8446, it says ...
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1answer
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TLS handshake with client later on acting as a server

Is it possible that a client which gets the Digital certificate of the Server during the TLS handshake then acts as a server? Because a server only needs to have a valid digital certificate which it ...
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TLS client authentication from static client image

I'm trying to implement mutual authentication for a TLS connection between a server (ONOS OpenFlow controller) and multiple clients (OpenFlow switches). I'm restricted in that I must create a single ...
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How is Pre Master Secret related to Client.random or Server.random if DH KEX is RSA

For TLS 1.2 cipher Suite AES256-GCM-SHA384, RSA is KEX(key exchagne algorithm). As per standards of RSA Diffie Hellman KEX, after 'ServerHello' message client gets server certificate and it generates ...
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Does SET in any way use SSL?

I just started a course in web security, and I was just wondering quickly if SET in any way would use SSL? I noticed it was developed in part by Netscape. But all I can find is comparisons between the ...
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1answer
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Is this pairing scheme for establishing trust between two devices with self-signed TLS certs secure from MITM?

Assume two devices (A and B) with self-signed TLS certificates (this part can't change). We want these devices to trust each other. One way to do this is to simply copy A's cert over to B's allowed ...
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1answer
287 views

Determining if Server/Client's TLS configuration is Vulnerable to SLOTH

In the context of SSL/TLS protocol and SLOTH vulnerability. I want to find out if certain websites(webservers) or applications that use TLS are vulnerable. I need some guidance for this. My idea is ...
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Does the Server Key Exchange sign a hash or text

In TLS 1.2 when using ECDHE_RSA, the ServerKeyExchange message contains a signature over the server's ECDHE public parameters. My question is: Is the signature over ...
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1answer
240 views

Does RSASSAPSS use RSA signature

I just need to know is it correct to classify the RSASSAPSS scheme and sha[256 | 512 | 1]WithRSAEncryption all under RSA ...
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1answer
712 views

What is Group in Diffie-Hellman?

I understand how Diffie-Hellman key-exchange works. Mainly, two parties agrees in a prime $p$ and a generator $g$. Then one party selects its private exponenet $x$, computes its public value $g^x \...
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1answer
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TLS handshake cryptography AES key query

I am working on a IoT project where I am trying to perform manual handshake (SSL) for certificates and sending data to the server securely using HTTPS POST method. RSA is used for sending Pre-master ...
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1answer
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RSASSA-PSS-SIGN modBits size

In RFC 8017 modBits is the length in bits of the RSA modulus n I am using 2048 RSA key ...
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2answers
3k views

Why is a Diffie-Hellman key exchange required when RSA is already being used for key exchange in TLS?

Specifically with TLS, What is RSA used for during key exchange? What is Diffie-Hellman used for? Since RSA already provides authenticity and confidentiality, why is Diffie-Hellman used during the ...
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4answers
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Is encrypted e-mail sent over TLS 1.3 a form of “forward secrecy” (similar to something like Signal)?

One common complaint about GPG-encrypted e-mail is that it doesn't provide forward secrecy; however with opportunistic TLS becoming increasingly common in both IMAP and SMTP, it's not unreasonable to ...
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1answer
528 views

Why Static RSA and Diffie-Hellman cipher suites have been removed in TLS 1.3?

Why Static RSA and Diffie-Hellman cipher suites have been removed in TLS 1.3? How keys can be exchanged then? https://tools.ietf.org/html/draft-ietf-tls-tls13-28
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2answers
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Does a trace of SSL packets provide a proof of data authenticity?

I'm wondering if it would make sense to record a whole HTTPS session, publish its encryption keys and present it to third parties as a proof that this particular data was sent by a given server ...
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TLS 1.3 Security against PKCS#1v1.5

This paper explains an attack on TLS 1.3. This was published way back in 2015 when TLS RFC was in draft stage. My question is now TLS 1.3 RFC is finalized, is this attack got addressed?
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Observing cipher suites and certificate algorithms without man-in-the-middle

I manage a proxy server. Is it technically possible to observe and determine which cipher suite is selected between end points (client and server) without changing their SSL certificate, without ...
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2answers
621 views

GMAC vs HMAC in message forgery and bandwidth

Saarinen in his work GCM, GHASH and Weak Keys says that: The GHASH algorithm belongs to a widely studied class of Wegman-Carter polynomial universal hashes. The security bounds known (this and ...
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1answer
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Cipher suites: same name, different IDs, why?

Sorry if I missed with a community to ask. Recently I stumbled on a fact that the same cipher suite can be designated by two different IDs, and this is not a typo nor single occasion. For instance: ...
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1answer
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Is it necessary to have a certificate when we use TLS

When we say a communication is secured by the latest version of TLS, can we say that Man-in-the-Middle attack is not possible? Do not consider the situations that we can down grade the communication ...
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3answers
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What is different below two Ciphersuites?

I have two questions; I need an explanation for the differences of below two cipher suites. How do they work with SSL/TLS protocol? (my main concern first one doesn't have '...
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1answer
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Why do we need HMAC?

AFAIK, HMAC solves the collision problem of hash algorithms by mixing in a pre shared secret. Can't we just use the pre shared secret to symmetrically encrypt data and leave out the hashing?
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How does tls 1.3 cope with man in the middle (in key exchange)

in case i cannot do PSK (give the same key to both sides via physical means). i saw tls1.3 still support DH (doesnt matter that it is DHE or ECDH). isnt that makes it a weak key exchange? do they ...
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A simple misunderstanding of SSL/TLS

I just came to learn about Deffie Hellman Key Exchange. And a little bit about RSA. I came to DH from something about SSL. From what I understood before is that SSL uses DH and TLS uses RSA, but after ...
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Size of Key Material of TLS_DHE_RSA_WITH_AES_256_CBC_SHA

What is the size of key material required for generating MAC keys, encryption keys and IV when use TLS_DHE_RSA_WITH_AES_256_CBC_SHA ? How to calculate it?
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Security of MAC-Then-Encrypt without MAC key authentication

We have the following settings in our system: TLS 1.2 using legacy cipher suite - OFB mode (using 64 bit block cipher) and trunkated CBC-MAC (32 bit). The goal is to achieve authenticated encryption ...
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1answer
70 views

TLS_DH_RSA_* cipher, how can static DH use an RSA certificate?

I am confused about TLS_DH_RSA_* ciphers because, for DH to work, the server certificate has to include a DH public key, but for server authentication the server certificate needs an RSA public key. ...
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SDES algorithm purpose

What is the purpose of SDES algorithm? (Session Description Protocol Security Descriptions) What are the problems in the way it exchanges keys? I have tried to search about these quastions but i ...
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Pitfalls of wildcard certificates with unique key pairs?

I am having difficulty finding information regarding using wildcard certificates with unique key pairs. I understand if you duplicate key pairs across multiple servers and one becomes compromised, an ...
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2answers
173 views

Talking TLS with EC cryptography and the secp256k1 curve [duplicate]

How reasonable would it be to speak TLS over the secp256k1 curve? My initial experiments show that OpenSSL supports it (albeit with special flags, see below): Running an OpenSSL client against an ...
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1answer
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Questions regarding static Diffie-Hellman (ephemeral-static) usage in TLS

It looks to me that there 3 main variants of Diffie-Hellman in SSL/TLS. Anonymous mode; Static mode; Ephemeral mode. In case of static DH the server owns an X.509 certificate with a DH public key ...
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2answers
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Why is it not possible to tap into the HTTPS traffic specifically going from the server to the client?

How I think HTTPS works when sending data from server to client: -Server has 1 public, 1 private key. -Client has access to the server's public key and not it's private key. -Client has no keys of ...
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1answer
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TLS Key Block calculation - What is a PRF?

In Section 6.3 of the RFC for TLS 1.2, it is written that the key_block is derived from the following formula: ...
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Does Openssl 1.1.1 library supports sending multiple identities as part of PSK?

Does Openssl 1.1.1 supports sending multiple ticket identities as part of PSK? i have gone through the openssl code and i don't see that openssl supports it. could someone please confirm it if i ...
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1answer
63 views

How are public keys securely and reliably obtained across the internet?

I've just decided to start learning all about PKIs, and I have come across what seems like a paradox. When fetching a public key from either a server or a CA, how can we be sure that the public key ...
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1answer
255 views

Static Diffie-Hellman in TLS

Static Diffie-Hellman (cipher suites with DH in their name but neither DHE or DH_anon - ...
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2answers
41k views

What's the difference between RSA and Diffie-Hellman? [duplicate]

I've been reading on a lot of websites that same thing: RSA is for communication using the public and private key for both the server and client, where Diffie-Hellman is just for exchanging the same ...
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2answers
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Differences between the terms “pre-master secret”, “master secret”, “private key”, and “shared secret”?

Both crypto.SE and security.SE have excellent Q&As about how TLS generates session keys (I have linked some at the bottom). In reading these threads I'm having troubles with terminology since the ...
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1answer
45 views

Generate a per data shared secret vs per session

I have read about SSL that they persist the shared-secret for the entire session. However, someone in stackoverflow suggested a way of generating a shared secret for each data to send and then send ...
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1answer
387 views

How does padding oracle attack work with bytes larger than possible length?

I am trying to understand how the POODLE attack would actually be implemented. In the original security advisory from Möller, Duong and Kotowicz [POODLE 14] the following example is presented: ...
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1answer
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Which TLS features are vulnerable to chosen-prefixes collision on SHA-1?

Gaëtan Leurent and Thomas Peyrin's preprint From Collisions to Chosen-Prefix Collisions - Application to Full SHA-1 (in volume 1 of proceedings of the forthcoming Eurocrypt 2019) shows a feasible ...
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2answers
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Why is PerfectForwardSecrecy considered OK, when it has same defects as salt-less password hashing?

PFS suites suffer from the same defects as any other salt-less password hashing scheme. Why is everyone promoting Perfect Forward Secrecy (PFS) ciphersuites so fiercely? Namely, when the group/hash ...
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1answer
193 views

Can the lengths of HTTPS requests be used to deduce which public pages on a site are visited?

I thought of this recently: There are some websites which have many publicly accessible pages, some of which could be embarrassing despite being public (e.g. Wikipedia). The HTML for these pages also ...
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Which parts of a TLS connection can I safely reuse for DTLS to the same peer?

Suppose I need both encrypted TCP and UDP, say TCP for reliable control signals from server to client and UDP for low latency data from client to server. If I first establish TLS, for the DTLS ...
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2answers
647 views

Using Lattice-based cryptography for TLS\SSL

Given the general benefits of Lattice-based cryptography, such as: Post quantum Security Security from worst case scenario Efficiency What could the outlook of shifting from RSA \ ECC-based ...
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1answer
250 views

How will be cipher selected when client is running on version TLS 1.3 and server is running on TLS 1.2?

How will be cipher selected when a client is running on version TLS 1.3 and server is running on TLS 1.2? The cipher list provided by TLS 1.3 client will be different than the version supported on ...
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1answer
755 views

The 9 lives of Bleichenbacher's CAT, it puts another scratch again

Bleichenbacher demonstrated a padding oracle attack against RSA implementations that follow the PKCS #1 v1.5. Through the years, there are various mitigation techniques developed as OAEP and limiting ...
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1answer
130 views

X.509 strong authentication protocols

Is there also a protocol definition in X.509? In "Handbook of Applied Cryptography" by A. Menezes there is a reference to X.509 strong authentication protocol, nevertheless, I could not find the ...
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1answer
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What key is used to encrypt the certificate and certificate verify message in TLS1.3?

Which key is used to encrypt certificate and certificate verify message in TLS1.3? I could not figure out which one it is reading section 4.4.2 of RFC 8846 and I only saw a vague mention on page 11.