Questions tagged [man-in-the-middle]

A man-in-the-middle (MITM) attack is an active attack where the attacker is able to interpose himself between the sender and receiver. The attacker may monitor and/or modify some or all of the messages sent between the two endpoints.

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23
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2answers
27k 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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3answers
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How to perform authentication without central server in P2P?

How can one be sure that the man who you're talking with is the one who you think he is? i.e. How can one perform authentication in P2P network without a central trust server or Certificate Authority? ...
11
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1answer
3k views

Is quantum key distribution safe against MITM attacks too?

i read this recently: http://www.newscientist.com/article/dn12786-quantum-cryptography-to-protect-swiss-election.html and some parts of this: http://en.wikipedia.org/wiki/Quantum_key_distribution ...
11
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0answers
268 views

The backdoor of Telegram on Diffie-Hellman Key Exchange and possible other examples?

Diffie-Hellman Key-Exchange (DHKE) should be used carefully during the end-to-end encryption. A man-in-the-middle (MITM) attack is possible. Standard DHKE The simple protocol on the multiplicative ...
9
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1answer
2k views

How can I attack a Triple-Block cipher with 2 keys (like 3DES) with a cost of ≤ 2⁵⁶

I am trying to solve something and I have but I have no idea anymore. Maybe anyone of you has an idea/solution/hint. Given is a block cipher $F$ with key length $n$. It looks like this: $$c = ENC_{k1}...
8
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1answer
8k views

What is difference between meet in the middle attack and man in the middle attack?

From my understanding man-in-the middle attack works as follow: Alice and Bob agreed to use Diffie-Hellman using $a$ and $q$. Alice sends $Y_A$. Before it reaches Bob, Charlie ...
7
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3answers
2k views

Vulnerabilities if encrypting the same data with 2 different keys

Let's say that Alice and Bob complete a key exchange and then Alice uses that key k1 to encrypt a 256-bit key kaes1 and sends it ...
6
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1answer
349 views

Proof that any key exchange protocol is vulnerable to MitM attacks in the absence of shared information or trust

Today I realised that every key exchange protocol I know, without a priori any shared information or trust relations (i.e. any ability to sign anything), is utterly broken by an active man in the ...
6
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1answer
349 views

What is 'Carry-forward verification' defense against MITM?

Wikipedia article on Man-in-the-middle attack mentions, in the list of defenses against it, some method called "Carry-forward verification", but it does not explain it. I am curious about different ...
6
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1answer
4k views

How does Bluetooth pairing (SSP with numeric comparison) work?

I have a question concerning the pairing of two Bluetooth devices using Simple Secure Pairing with numeric comparison. The NIST document I am looking at states on page 14: Numeric Comparison was ...
5
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4answers
19k views

Diffie-Hellman and man-in-the-middle attacks

See here for the man-in-the-middle attack on Diffie-Hellman that I'm concerned about: What is Diffie-Hellman? How do we combat this? I have two questions: Is one solution for both Alice and Bob just ...
5
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3answers
2k views

Is this Diffie-Hellman key exchange variant vulnerable to man-in-the-middle attacks?

As we all know, the Diffie-Hellman key exchange protocol without authentication is vulnerable to a man-in-the-middle attack. And if we use STS(Station-to-Station protocol) instead, it would be secure. ...
5
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4answers
9k views

Diffie-Hellman Key Exchange with Authentication: Man-in-the-Middle query

I have been reading up on MiTM attacks, and the prevention of them using public key certificates. Recently I learnt about Diffie-Hellman Key Exchange with Authentication, and how it uses signed ...
5
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0answers
139 views

Multilinear trapdoor commitments secure against concurrent man-in-the-middle attacks

I am trying to understand how to apply a multi-trapdoor commitment described by Gennaro and what makes them secure against a concurrent MiM attack. There are two ways to construct a multi-trapdoor ...
4
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4answers
407 views

Can cryptography be used to hide routing information from the router?

If Alice wants to talk to Bob and she has to involve a third party system run by Carol to establish, and possibly maintain, communications, then Carol knows that Alice and Bob communicated with each ...
4
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1answer
757 views

Why is SRP considered to be resistant to MITM attack?

Why is SRP considered to be resistant to MITM attack? Documentation says A man-in-the-middle attack, which requires an attacker to fool both sides of a legitimate conversation, cannot be carried ...
4
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2answers
923 views

Curve25519 - Alice can decrypt her own message to Bob?

I'm developing an application with multiple clients and one server. All clients will have the same hard-coded Curve25519 key pair as well as the server's public key. The server will have its own key ...
4
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2answers
2k 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 ...
4
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1answer
82 views

Why are some websites seemingly immune to self-signed certificate MitM attacks?

I recently did an experiment using MitM to gain account information (username and password) while accessing websites. I used two PCs in the scenario; one as the target, running Internet Explorer, and ...
4
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1answer
4k views

What are the problems of IKEv1 aggressive mode (compared to IKEv1 main mode or IKEv2)?

I would like to seek confirmation/clarification of the following statements about IKE: IKEv1 aggressive mode is supposed to be “insecure” if used with PSK. But as far as I can see, correct (or more ...
4
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1answer
135 views

possible MITM attack against servers that used to support weak DH?

from reading the TLS 1.1 RFC, it looks like it would be possible to break a previously recorded TLS <1.2, 512-bit DHE ServerKeyExchange and then send it (unmodified, with the original, valid ...
3
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2answers
503 views

Please punch holes in this authentication scheme

Folks, I am undertaking a crypto course in Uni. Our professor asked us to try and design some authentication schemes which are resistant to active attacks. This was just a in class exercise to get us ...
3
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1answer
883 views

In Diffie-Hellman, can everything be sent in plaintext?

I think my limited understanding of DH might be messed up - what's wrong with this scenario? C wants to connect to S. C has an ECDSA public key that it trusts belongs to S. Here's what happens: C ...
3
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2answers
177 views

Self authenticating tamper resistant first meetings

I'm not sure what the precise words I am looking for are so I apologize if there is a better way to phrase this. What I am thinking of is ways to transfer an identity in a way that it is tamper ...
3
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1answer
5k views

MiTM on RSA public key encryption

a) Alice just generated a new pair of public and private RSA keys (pkA , skA ) = ((N, e), d) and would like to start a private conversation with Bob. How can Alice interact with Bob and exchange a ...
3
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1answer
295 views

SRP and compromised verifier [closed]

Let's assume that attacker knows the verifier so now the attacker can commit a Man-in-the-Middle (MitM) attack: Client sends A to server; MitM takes it and sends B to client. As the MitM knows the ...
3
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1answer
800 views

How does the small n attack work?

I'm studying the Lamport's Hash one-time password scheme. This is the scheme: Alice wants to authenticate herself to Bob from a workstation that knows nothing about her. Alice only knows her ...
3
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1answer
1k views

Man-in-the-middle attack on Diffie-Hellman with shared public keys?

Is it correct to say if the public key is known to all users beforehand, Diffie-Hellman key exchange is not vulnerable to man in the middle attack? Sample key exchange ( assuming all users public ...
3
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1answer
713 views

Do ECDH and ECDSA combined solution provide an authenticated protocol exchange solution in MCU environment?

I'm working on a project in MCU (micro controller) environment with GPRS connection to exchange data securely with the cloud. The encryption algorithm has been selected to use AES. I did some search ...
3
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1answer
433 views

What is the impact of a server not fully verifying the data in the Client Finished packet of a TLS connection?

F5 BIG-IP devices suffer from a vulnerability in which not all bytes of the Finished packet in a TLS connection are validated. The sort-of technical description can be found here. F5 don't consider it ...
3
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1answer
972 views

Key exchange and man in the middle issue. Secure solution

I am trying to design MiTM protected key exchange algorithm. For instance I am using RSA asymmetric keys. Alice and Bob respectively have each their own pair of keys. And they should be able to ...
3
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0answers
167 views

Is the “Pico” alternative to passwords vulnerable to man-in-the-middle?

Maybe someone has already heard about "Pico" by Frank Stajano. In short: It is a model for an alternative for using passwords for authentication and seems to be very interesting. Regarding the paper, ...
3
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0answers
189 views

Is MITM possible after key exchange phase done successfully in RSA?

Is MITM attack theoretically possible after public/private key pair exchange is done successfully? Say Alice and Bob have genuine public keys of each other. Is MITM possible further during the ...
2
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1answer
4k views

ECDH Man-in-the-middle active attack

We have Alice and Bob. The man in the middle can manipulate(remove, add something etc.) A sent from Alice and B sent from Bob, how can he figure out what the common key K(A,B) is, without knowing kpr(...
2
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1answer
144 views

How is Diffle Hellman with RSA immune to man in the middle?

Alice and Bob want to exchange keys, Alice sends his half (the public key of the ephemeral key pair) signed with his private key and makes the public key available. Eve is bridging the connection so ...
2
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3answers
2k views

Diffie-Hellman algorithm and MITM attack

How does the Diffie-Hellman algorithm prevent MITM attack? I have tried to search about it but i couldn't find any understandable reasons.
2
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3answers
95 views

Is there a method/protocol to validate a self-signed certificate by comparing a shortened hash?

I'm working on a solution where an iPad should connect to a server software running on a laptop using TLS with a self-signed certificate that was automatically generated on the laptop during the ...
2
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5answers
852 views
2
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1answer
413 views

Government root SSL certificate possible vulnerabilities [closed]

I'm writing an article about new government law in Kazakhstan. The law was accepted in December, but now one of our providers announced information for small and medium business how to install ...
2
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2answers
299 views

Security of S/MIME in case of CA compromise

Suppose Alice and Bob are exchanging messages using S/MIME, protected by certificates that have been issued by either the same CA or by two mutually independent CAs. There exists an adversary Mallory ...
2
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1answer
44 views

Dishonest verifier running a concurrent zero-knowledge protocol

Suppose Alice and Bob are engaged in the graph 3-colorability Zero-knowledge protocol in which Alice permutes a coloring $\varphi:V\rightarrow \{1,2,3\}$ for a graph $G(V,E)$, and then sends a ...
2
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1answer
68 views

MitM with regard to unauthenticated clients

I'm trying to understand how man-in-the-middle attacks are prevented during key exchanges, and am confused by this Wikipedia statement: Use of mutual authentication, in which both the server and the ...
2
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1answer
366 views

Interlock Protocol for Preventing Man-in-the-Middle (MitM) Attack

Trying to turn bookish knowledge to practical: Alice sends half of the encrypted data to eve, eve eavesdrop and tries to decrypt the data and fails as eve has only half of the encrypted block. So, ...
2
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2answers
163 views

Transmit half the bits of the $g^a$ and $g^b$ as MITM countermeasure in DH key exchange?

I remember this trick from one of my crypto courses way back then, but I can't find the details, and I'm unable to figure out the logic behind it. I'm talking about a countermeasure to the MITM ...
2
votes
1answer
91 views

Can the original message be retrieved from a public/private key signature?

When I sign a message (which has potentialy low entropy) using a private key and I send it without the original message, can the original message be retrieved from the signature(s)? I want to prove – ...
2
votes
1answer
615 views

Is there really any way to nullify or avoid MITM attacks?

The question pretty much sums it up. Is there any way to make an attacker who is successfully performing an MITM attack to actually not be able to read or change the messages? Assuming there is no ...
2
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2answers
277 views

How can A pass a message to B, while preventing a third party from sniffing infos?

$A$ has a message that he wants to send to $B$, without a third party being able to learn the contents of the original message. $A$ encrypts the message and sends it to a server. The server decrypts ...
2
votes
1answer
237 views

Man-in-the-middle attack on text-book RSA PKE

I am attempting to solve the following problem: I know the following: 3 messages are being sent between Alice and Bob, all messages are encrypted with the known public key $(d,N)$: Alice sends ...
2
votes
2answers
1k views

Prevent MITM attack while encrypting data by using ElGamal ECC?

I am using ElGamal ECC to encrypt my plain text data. I want to ensure that my data is safe from a Man-In-The-Middle attack. What methodology I can adopt to achieve this goal? How can we prevent a ...
2
votes
1answer
216 views

DH key exchange with only one end authenticated

We know there is a man in the middle vulnerability with unauthenticated DH key establishment. And the way to negate that is to use authenticate the keys used. But what if I only verify the signature ...