Tagged Questions

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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Random numbers for Master Key and Key_block

Exploration through RFCs concludes that random numbers used in the creation of Master Key and Key Block(Key material for Encryption Key and Mac Secret) are from ServerHello.random and ...
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0answers
98 views

Should layered use of crypto always have a cryptographic binding between the layers?

Reading the latest TLS weakness, it seems that multiple weaknesses have been found over the years caused by not ensuring that messages are sent over the same channel, and in general a lack of ...
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4answers
632 views

How does TLS generate the shared secret?

From many readings, I got to know that TLS generates master shared secrets using pre-master keys and uses the DH algorithm to generate the shared secret/Master secret. What values during the hello ...
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1answer
85 views

Do both client and server need to implement OpenSSL protections to protect from CBC attacks

In regards to the protections implemented in OpenSSL 0.9.6d (described in section 2. http://www.openssl.org/~bodo/tls-cbc.txt). My understanding is that the mechanism prepends an empty record when ...
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1answer
173 views

TLS: Is Integrity assured when using NULL cipher

In specific implementation we're using TLS 1.0, open ssl 0.9.8 but i'm referring to RFC 5246. For performance reasons, I'm being asked if we can use TLS without encryption. The hope is that the ...
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2answers
257 views

What was the problem in the SSL version 2.0?

What is the main reason (attacks) the appearance of the protocol SSL version 2.0 to replace version 3.0?
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2answers
503 views

At what stage is DHE and RSA used during the SSL/TLS handshake?

At what stage of the SSL/TLS handshake is the DHE and RSA used and what is the purpose of using a pre-master secret when you could just use RSA to exchange the symmetric key (i.e. AES) for further ...
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2answers
330 views

Where is my private key stored when I communicate to a website that uses SSL/TLS?

If I communicate with a website that uses SSL/TLS, my browser will generate a private key. Would the browser store that key on the hard disk or would store just it in the RAM?
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3answers
297 views

Is SSL broken? If so, what can I do about it? [closed]

But recently, with the scandals about the (in)filtrations, I read that the NSA (and of course others, but I'm not particularly worried about NSA) is able to break SSL and track your data. It is true? ...
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3answers
220 views

Is the following authentication protocol insecure?

I am a student taking cryptography this semester. I was just wondering why can't we use this simple protocol? Alice → Open Connection → Bob Alice ← Cert$_b$ ← Bob Alice → {K$_{AB}$}$_{Bob}$ → Bob ...
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2answers
102 views

Could someone reuse client certificates?

To my understanding, if a server “cert+key” (RSA) is compromised, than the SSL/TLS network traffic can be decrypted. What about a client “cert+key” (RSA)? Could someone reuse client certificates? ...
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0answers
90 views

Is it possible to modify SSL handshakes to enable PFS while still using RSA during the handshake?

I know we could possibly be using DH key exchange, that would enable PFS. However, what if we make modifications on our SSL 3.0 handshake such that the only cipher we use is RSA for the achieving PFS? ...
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1answer
1k views

Does ssl_rsa_with_rc4_128_md5 have known weaknesses?

My bank's website uses HTTPS with the cipher suite ssl_rsa_with_rc4_128_md5. What are the known weaknesses of this suite? Do they have a practical impact for ...
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2answers
210 views

Cryptanalysis and weaknesses of SEED cipher

I've discovered that a client has SEED enabled in their SSL ciphers, and would like to know a bit more about it from a security perspective. The Wikipedia article doesn't mention any flaws, yet I've ...
2
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1answer
119 views

How does SSL secure the initial handshake?

I'm reading the SSL specs, and it seems that the initial handshake has no authenticity protection at all. What is to prevent, say, an attacker from overwriting the "available ciphers" list with one ...
2
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3answers
250 views

OFB or CTR mode without an IV

I'm reading the SSL specs here. The interesting thing seems to be that RC4 is not re-keyed with a new IV for each message. The stream cipher state is simply carried over to the next record. Why is ...
1
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1answer
176 views

With TLS and ECDHE, how does curve selection work?

Given that a TLS client and server have already agreed upon ECDHE for session key establishment, how does the selection of the actual elliptic curve ("domain parameters") being used for deriving the ...
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2answers
2k views

With OpenSSL and ECDHE, how to show the actual curve being used?

Using openssl s_client -host myserver.net -port 443 I can see the cipher negotiated is indeed using ECDHE for session key ...
7
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1answer
486 views

What is wrong with AES-CTR-HMAC-SHA256 - or why is it not in TLS?

It seems the only specified CTR mode ciphers in TLS are all GCM based. GCM ciphers run AES-CTR and do authenticated encryption with a MAC based on Galois-field ...
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2answers
1k views

Which stream cipher can we replace the RC4 in the SSL?

In cryptography, the Fluhrer, Mantin and Shamir attack is a particular stream cipher attack, a dedicated form of cryptanalysis for attacking the widely-used stream cipher RC4. The attack allows an ...
2
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1answer
351 views

How do TLS 1.1 and 1.2 generate IVs (initialization vectors) for each record?

According to RFC 4346 Explicit IVs [CBCATT] describes a chosen plaintext attack on TLS that depends on knowing the IV for a record. Previous versions of TLS [TLS1.0] used the CBC ...
2
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1answer
229 views

Verifying Self-signed SSL Client Certificates

I have a service and I want to authenticate my clients using SSL client certificates. Now I want the key exchange process to be as simple as possible, kind of like SSH: You generate a keypair and ...
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2answers
3k views

Why is TLS susceptible to protocol downgrade attacks?

A recent blog post from Ivan Ristić (expert extraordinaire on all things SSL) says: all major browsers are susceptible to protocol downgrade attacks; an active MITM can simulate failure conditions ...
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1answer
770 views

Possible ECC backdoor and its impact on Internet traffic

In a recent article, Bruce Schneier suggested that he prefers classic discrete log crypto over ECC because "I no longer trust the constants. I believe the NSA has manipulated them through their ...
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2answers
457 views

Camellia or AES - which should I use?

Imagine I am a software developer. I want a block cipher, and I have the choice of using AES or Camellia. Which should I use? Which makes more sense from a technical perspective, and why? I need ...
2
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0answers
79 views

Could BREACH be used to determine an HTTPS URL?

I was reading this article and had a question.... http://arstechnica.com/security/2013/08/gone-in-30-seconds-new-attack-plucks-secrets-from-https-protected-pages/ As I understand it TLS/SSL work in ...
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5answers
28k views

Technical feasibility of decrypting https by replacing the computer's PRNG

Intel has an on-chip RdRand function which supposedly bypasses the normally used entropy pool for /dev/urandom and directly injects output. Now rumors are going on that Intel works together with the ...
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1answer
113 views

how does https key get shared?

I am only a beginner and doesn't know much about https. I have heard that they uses somekind of a key and is shared between them. If an attacker wishes to attack could he be able to capturebthe key ...
2
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1answer
217 views

Are SSL modes with forward secrecy vulnerable to the BEAST attack?

From the original BEAST paper, it seems to me that you need the same session key when encrypting data, so you can check if the original plaintext block is the same as your chosen plaintext (which is ...
1
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0answers
111 views

openssl logs showing keyblock length of only 88 bytes instead of 136 bytes

I was decrypting TLS encrypted data from wireshark using the openssl(TLS1.0 version) TLS logs which provides the complete key block which of size 136 bytes.Now i moved to TLS(1.2 version) in that Key ...
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1answer
535 views

Sending TLS messages with out encryption using openssl code

Is it possible to send messages over TLS with out encryption? If so which cipher suite is needed for this?
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3answers
20k views

How can I use SSL/TLS with Perfect Forward Secrecy?

I'm new to the field of cryptography, but I want to make the web a better web by setting up the sites that I host with Perfect Forward Secrecy. I have a list of questions regarding the setup of ...
1
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1answer
134 views

What should the size of the private exponents in Diffie-Hellman key exchange for TLS be? [duplicate]

I'm using TLS with a Diffie-Hellman key exchange to negotiate the symmetric keys. How long should the exponents be?
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2answers
190 views

How is SSL secure from rogue Certificate Authorities?

There's one thing that I've never quite understood about SSL (which perhaps means I don't understand SSL at all): how is SSL secure from rogue Certificate Authorities? This is probably best ...
5
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1answer
220 views

Why is TLS SRP verifier based on user name?

I don't understand why TLS SRP (or SRP in general) includes the user name in verifier calculation, given that user name is basically public. From spec RFC 5054 $x$, which is then used to calculate ...
1
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1answer
152 views

Which keys are necessary to decrypt Application data in a SSL connection?

I'm debugging an application which communicates between client and server using a SSL/TLS connection, and want to capture and analyze the sent data. Are the client write keys and server write keys ...
2
votes
2answers
444 views

What are the potential security impacts of using CRAM-MD5 for Emails, when not using an SSL connection?

Background: My current server-provider tells me it's no problem to store the passwords in plain-text in the database, saying he has to do so because they use CRAM-MD5 for email authentication. But ...
2
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2answers
312 views

Generating IV in TLS 1.2

I'm writing a TLS 1.2 implementation (in C#) using a custom protocol. My question is how to generate the IV attached to each message, I don't want to use RandonNumberGenerator because I've heard it ...
4
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1answer
392 views

Client and server using same SSL certificate - any issues?

I'm working on software where multiple components will communicate with each other using SSL. There would be one central component acting as a server, which would also require the clients to present ...
5
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1answer
133 views

Using encryption schemes for identification

I've been researching how to implement a post-quantum SSL-like connection authentication, especially correct identification&authentization of the server/client. Because good post-quantum digital ...
10
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1answer
2k views

Why is CAMELLIA suddenly so widely used?

When nowadays I point my browser to https sites, the cipher that is on most occasions used is Camellia. My browsers (Chrome and Firefox) seem to prefer it, even when AES is available. Is that not ...
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0answers
1k views

Cryptographic Protocol using NaCl

Why? I wanted to add some security and privacy to a chat-type server for playing various games (with a few things that are done on the server to limit cheating). Going by the "Don't implement ...
3
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1answer
259 views

Is there a field guide to ECC for the IT Security layman?

I'm trying to understand ECC from an IT layman's perspective and am trying to separate the theory from the standards, and understand why certain features are implemented or not implemented in the ...
3
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1answer
156 views

SSL Key Exchange

I read briefly over the TSL/SSL key exchange protocol. I have to wonder about the whole pre-master-key procedure. Wouldn't it be sufficient if the client or server encrypted a generated session key ...
5
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2answers
708 views

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 ...
1
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1answer
1k views

How does a client verify a server certificate?

As far as I know, when I request a certificate from Verisign (for example), and after they approved that me is me, they create a certificate (for me) which contains the digital signature and public ...
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4answers
692 views

Would this simple encrypted chat program be feasible using One Time Pads?

Lets say I want to build a simple chat program that has encryption that is impossible to crack for anyone, even a theoretical government with a massive super computer. Ok here's my idea. You'll need ...
4
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1answer
502 views

is this RSA private key valid?

is this RSA private key valid? First, here's the RSA private key in question: ...
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2answers
263 views

The security of data traffic over both SSTP & SSL

Suppose you're connected to a VPN server via an SSTP VPN, and then you're trying to sign in to your webmail account that is already secured with an SSL certificate, e.g. hushmail.com. However, it ...
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2answers
356 views

Is RC4 a problem for password-based authentication?

This is a follow-up question to Does TLS use RC4-drop[n]?. As mentioned in section 6 of RFC4345, there are weak distinguishers for RC4 keystreams available that even work for keystreams that ...