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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1answer
77 views

What should be broken to break a cipher with perfect forward secrecy?

What should be broken to break a cipher with perfect forward secrecy as a passive observer? RSA/EC analog, (EC)DHE or both?
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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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0answers
64 views

Are there any one-way operations that could be used for Diffie-Hellman post-quantum? (See criteria)

With quantum-computers looming, there is a need for Public Key Cryptosystems that can withstand attacks by quantum-computers. Are there any known one-way operations that fit the following criteria? ...
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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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1answer
77 views

What 32 bytes TLS data records for?

I've captured my tor client network traffic and noticed that in every packet it sends 2 TLS records first of which is always 32 bytes long. The first TLS record seems not to be carrying any data. What ...
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3answers
160 views

Is this a correct SSL explanation in layman's terms?

I'm looking to provide a basic / layman's explanation of SSLs to clients and want to be sure it is correct. My explanation is below and would appreciate any feedback / corrections. Basically, the ...
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0answers
49 views

MAC with key supplied afterwards

Looking at HMAC and KMAC it seems that the key is always required up front, i.e. before starting to process any other data. However, in many protocols the key may not be known it advance. For instance,...
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1answer
70 views

SSL and first step of handshaking

When I connect to a secure sever that has is equipped with SSL certificate. Logically, the first step is the handshake to discuss the cipher suites etc. However, the very first time my web browser ...
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1answer
5k views

IPSec vs SSL : Similarities and Differences

I am studying SSL and IPSec. I can pretty much nail down the "very high level" differences and similarities between the two, but am struggling to find a "lower level" (but not too deep) look. This ...
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1answer
435 views

How is a fake private key used in CloudHSM?

I've noticed that AWS CloudHSM uses an openssl command to generate a fake private key for web servers that offloads cryptographic functions to a CloudHSM. How does this key work? And what purpose does ...
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1answer
139 views

What does GHASH really do?

I try to understand the GCM-MODE used in TLS. The problem I have had is described below. 1:textbook describes how GHASH works: 2: I get some debuginfo from openssl code that contain enc_key(32 bytes)...
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1answer
119 views

What kind of ciphers does not depend on order of operation?

What kind of cipher does not depend on order of operation ? For Instance if we have two operations encryption Enc(m,k), decryption Dec(m,k) and some message m. For which ciphers the following is ...
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1answer
74 views

CAs are pre-loaded on the system, but how is it able to get intermediate certs?

I have the following X509 certificate: ...
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1answer
947 views

What role does RSA play in DHE_RSA cipher suite?

I've read in this article, that encrypting a premaster key with a RSA public key is not safe from forward secrecy attacks. If an adversary, records all communication between a client and a server. And ...
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1answer
952 views

What is the Peer Signing digest on an OpenSSL s_client connection?

For a little background, I am trying resolve an issue with an ISAM (reverse proxy) appliance not being able to connect to a server due to it failing to complete a TLS connection. A server that is ...
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1answer
236 views

TLS false start / early data

How often such mechanisms are used by application. Is it real requirement to support these features for TLS ?
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0answers
56 views

Custom encryption scheme for SSL

Suppose that messages transmitted over SSL are modified as follows: the message is splitted in blocks, $B_1, ..., B_m$ (each with at most $2^{14}$ bytes) for each block $B_i$ we do: ...
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2answers
1k views

TLS re-negotiation vs resumption

Please explain the difference between TLS re-negotiation and resumption. My understanding is as follows: in the context of TLS 1.2, re-negotiation and resumption look the same, but the former can be ...
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1answer
415 views

How does Naver Line PC client obtain private key for end-to-end encryption (letter-sealing)?

When I download Naver Line PC client onto my PC, a six-digit number will be shown on the PC client for me to enter the number into my Line app on my mobile phone for decrypting the old and new ...
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1answer
49 views

Tls 1.3 ClientHello legacy_session_id as zero length vector alignment

Looking at tls 1.3 draft 23: https://tools.ietf.org/html/draft-ietf-tls-tls13-23 Section 4.1.2 shows, for a freshly established connection (no previous session from tls 1.2 or earlier) the ...
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1answer
702 views

What is the difference between these two TLS suites?

I am comparing the security information of two different HTTPS connections in the Google Chrome (v63.0.3239.132) security tab in developer tools. The information for each of the two connections is ...
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1answer
916 views

Raw public keys vs PSK in TLS

Is there any advantage in using raw public keys (RFC 7250) in comparison with pre-shared keys (RFC 4279) in TLS, when I need client authentication and have an unique key per client deployed to them ...
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0answers
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Implications of TLS-SRP client with improper N validation?

During development of a client side application of TLS-SRP, i noticed a bug that allows an attacker spoofing as the server to send custom, but non-arbitrary $N$ values, with the client accepting them. ...
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1answer
258 views

Interpreting the Hash type in a TLS ciphersuite

There are ciphersuites with SHA256, and SHA384. In the following TLS ciphersuite, the SHA types is not specified. Does this always refer to SHA1 (there is SHA0 as well) so which one of them? ...
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1answer
1k views

how to validate cert when signed cert has authority key id but signing cert doesn't?

Say I have the following signing cert: ...
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0answers
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Does TLS 1.3 really send PSKs encrypted?

In the following link it says: When a 1.3 client connects to a 1.3 server they agree on a resumption key (or PSK, pre-shared key), and the server gives the client a Session Ticket that will help it ...
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8answers
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Why is SSL on top of TCP?

Why is SSL not under TCP (the Transport layer)?
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1answer
846 views

What are the major differences between SET and SSL?

SET and SSL are usually used as secure payment protocols. What are the major differences between them? Which one is better?
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1answer
770 views

TLS Handshake with DH

I try to understand the TLS Handshake with DH. I googled the concepts and I think I understood the basics. But there are somethings I'm still struggling with. I also read the following two posts Why ...
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1answer
568 views

How does HTTPS transfer the symmetric key?

How is the server's public key used to encrypt the symmetric key in a way so that only the sever's private key can decrypt the cipher? The client uses the server’s public key to encrypt the ...
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1answer
152 views

Cut through mode for TLS AES-CBC / SHA ciphersuite

I am looking at RFC5246 and it seems that AES-CBC/SHA cipher suites cannot be implemented in a cut-through mode. Let's suppose that received record spans two segments. As i understood HMAC ...
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2answers
114 views

What data Certificate Authority encrypt for CSR?

I have been searching for a detailed explanation but can’t seem to find a low level one. 1) When CA sign the data with its private key, the encrypted data is APPENED to the csr or the whole cert ...
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1answer
198 views

Digital certificate issuing man-in-the-middle attack

While obtaining digital certificate the applicant trusts the certificate authority (or registering authority) as CA is digitally certified (and applicant has CA's public key). To certify a domain ...
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2answers
659 views

How does registration authority verify entity's identity for SSL? [closed]

In the answer here: Verification of identity by certification authority, it states that for European eIdentity you must provide your passport or ID card, but that this practice is quite different ...
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3answers
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Why was AES CBC removed in TLS 1.3?

I don't quite understand why AES CBC was removed in TLS1.3 . from what I know CBC is the most secure Mode of operation for the AES block cipher ( if you can say it like that ) It only needs a TRND IV ...
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1answer
337 views

What order should these HTTPS ciphers go in to maximize security?

I want to set up a very secure-from-MITM-attacks server. I have these algorithms enabled in my nginx and I'm getting an A+ on ssllabs.com but it's complaining that my cipher strength isn't 100% and ...
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1answer
41 views

What is the default behaviour, if no ciphers are enabled

Lets assume for example, that a server is configured to use TLS 1.0 and there are no ciphers enabled for it. What will be the default behaviour if a client connects to it? Will the server use any ...
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1answer
228 views

How HMAC is calculated for TLS AES_128_CBC_SHA

The RFC 5246 defines generic block cipher as follow: struct { opaque IV[SecurityParameters.record_iv_length]; ...
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1answer
127 views

Changing the public key in an MD5 certificate

Given a valid, signed X.509 certificate using the MD5 digest algorithm and an RSA public key, how feasible would it be to generate a public key which would, all other parts of the certificate being ...
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1answer
305 views

SHA2 Certificate generating (create Signed Certificate) [closed]

i was requested to write a programmer that can generate A SHA2 certificate. So i wrote a tester class to try and mimic Keytool process of generating One (referencing base of this: url https://www....
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2answers
22k views

Is Triple DES still considered safe to use?

What it says on the tin. Is it still used in things like TLS?
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1answer
131 views

Can we use higher strength SHA along with lower strength RSA key in SSL?

I have noticed when the RSA public key is 2048 bit, SHA-256 bit used for signatures. When the key is 3072 bit, SHA-384 bit used. When the key is 4096 bit, SHA-512 bit used. I have tried the ...
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1answer
103 views

For TLS AES_CCM mode how does CBC_MAC work when the message length is not aligned to block size?

Even after goign through lot of specs I failed to understand how CBC-MAC works, specifically in case we have message not aligned to 16 bytes. Are there any padding bytes?
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1answer
339 views

TLS AES_XXX_CCM mode of operation is encrypt-then-mac or mac-then-encrypt?

There are number of definitions completely confusing me. in https://en.wikipedia.org/wiki/CCM_mode we have "As the name suggests, CCM mode combines the well known CBC-MAC with the well known counter ...
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1answer
215 views

The parameters included in TLS 1.2 server signature in the ServerKeyExchange

In TLS 1.2, section 7.4.3 in the standard documentation on Server Key Exchange Message, it says that the parameters covered by ...
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4answers
1k views

The difference between MACs vs. HMACs vs. PRFs

I have some confusion regarding the difference between MACs and HMACs and PRFs and when to use which term. If the function is computed using a hash and secret key like the following, is this a HMAC ...
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1answer
1k views

Clarification needed in TLS 1.2 key derivation process

Reference to TLS 1.2 standard documentation section 6.3 regarding the key generation here: To generate the key material, compute ...
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1answer
970 views

The number of keys generated in TLS 1.2?

In section 6.3. Key Calculation in the standard documentation here, I see the following: The master secret is expanded into a sequence of secure bytes, which is then split to a client write MAC ...
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1answer
569 views

Is TLS 1.2 compression methods in client_hello a mandatory field?

As stated int he question, is compression methods list in the client_hello in TLS 1.2 a mandatory field (it is clear that it is mandatory in session_resumption, but not clear to me whether it is ...
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2answers
613 views

TLS Finished message: is it MAC or HMAC

In several academic literature, the term Finished MACs is used frequently. I wonder, is it really a MAC or HMAC? I am looking at literature in TLS 1.2 vs. TLS 1.2 specs. The specs of TLS 1.2 Finished ...