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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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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 ...
D.W.'s user avatar
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14 votes
0 answers
942 views

The backdoor of Telegram on Diffie-Hellman Key Exchange and possibly 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 ...
kelalaka's user avatar
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12 votes
3 answers
6k views

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? ...
Abzac's user avatar
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11 votes
1 answer
4k 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 ...
H M's user avatar
  • 283
10 votes
8 answers
1k views

Does humanly verifiable one time pad authentication exist?

Firstly some predicates:- Sufficient hardware generated one time pad key material. No pad reuse. Messages of 160 characters length (think Twitter). 28 characters only in use (A-Z, space and full stop ...
Paul Uszak's user avatar
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9 votes
3 answers
3k 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 ...
Jeff's user avatar
  • 193
9 votes
1 answer
3k 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}...
Donut's user avatar
  • 395
8 votes
1 answer
11k 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 ...
James's user avatar
  • 171
6 votes
1 answer
425 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 ...
E. Postlethwaite's user avatar
6 votes
1 answer
5k 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 ...
Shan-x's user avatar
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6 votes
1 answer
357 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 ...
catpnosis's user avatar
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5 votes
3 answers
7k 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.
Mas HJ's user avatar
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5 votes
4 answers
21k 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 ...
Luke's user avatar
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5 votes
3 answers
3k 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. ...
Nathaniel's user avatar
  • 153
5 votes
2 answers
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 ...
King Spook's user avatar
5 votes
0 answers
176 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 ...
omnomnom's user avatar
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4 votes
4 answers
429 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 ...
Adam Davis's user avatar
4 votes
1 answer
845 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 ...
Tony's user avatar
  • 277
4 votes
2 answers
1k 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 ...
TimH - Codidact's user avatar
4 votes
4 answers
10k 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 ...
user10941's user avatar
4 votes
1 answer
96 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 ...
Pierrot's user avatar
  • 143
4 votes
1 answer
1k 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 ...
Loris's user avatar
  • 225
4 votes
1 answer
5k 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 ...
Robert Siemer's user avatar
4 votes
1 answer
150 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 ...
lily wilson's user avatar
3 votes
1 answer
5k 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(...
Sick654's user avatar
  • 31
3 votes
1 answer
230 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 ...
Gaurav Pant's user avatar
3 votes
2 answers
575 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 ...
sukhvir's user avatar
  • 245
3 votes
1 answer
1k 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 ...
user avatar
3 votes
2 answers
183 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 ...
Zimm3r's user avatar
  • 295
3 votes
3 answers
486 views

Public-key/asymmetric encryption where you can only leak the decrypted message by leaking your password

A bunch of friends are using public-key encryption to send encrypted messages to each other using an open public forum. I.e. each friend has a public key (which you can use to encrypt messages for ...
chausies's user avatar
  • 335
3 votes
1 answer
6k 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 ...
santteegt's user avatar
3 votes
1 answer
322 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 ...
Tony's user avatar
  • 277
3 votes
2 answers
298 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 ...
Lee's user avatar
  • 153
3 votes
1 answer
428 views

Are there any protocols that are truly secure from active and passive MITM attacks?

Are there are any cryptographic protocols or algorithms that can prevent active MITM attacks or interference when initiating a new connection to a server or someone you have not exchange keys with ...
user31425's user avatar
3 votes
1 answer
2k 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 ...
newbiecrypto123's user avatar
3 votes
1 answer
859 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 ...
Johnny Shao's user avatar
3 votes
1 answer
480 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 ...
Polynomial's user avatar
  • 3,527
3 votes
1 answer
1k 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 ...
Alexey Kamenskiy's user avatar
3 votes
0 answers
373 views

TLS 1.3 Handshake - Usage of MAC and Digital Signature for CertificateVerify and Finished Message

I was wondering, why the TLS 1.3 handshake employs two different 'messages' that compute an authentication code over the whole handshake. As far as I understand, the CertificateVerify "message&...
Bastian's user avatar
  • 31
3 votes
0 answers
174 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, ...
chris000r's user avatar
  • 519
3 votes
0 answers
197 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 ...
user40349's user avatar
2 votes
3 answers
170 views

Can a man in the middle tell what kind of encryption you're using from a key exchange?

Encryption schemes typically are built on the idea that even if a man in the middle attacker knows exactly what kind of encryption you're using, they cannot decrypt your messages without the key. ...
Beefster's user avatar
  • 121
2 votes
5 answers
1k views

Is use of pre-shared key for sharing session key in symmetric key cryptography vulnerable to MITM?

Consider the following protocol: ...
user40349's user avatar
2 votes
2 answers
2k views

Does key authentication in SSH protect from MitM?

How do cryptography in SSH(2) work (secure channel establishment, authentication)? Does key authentication in SSH(2) protect from MitM by providing authentication and integrity and why?
Smit Johnth's user avatar
  • 1,691
2 votes
2 answers
989 views

Does DTLS in WebRTC protect from active Man-in-the-Middle?

I wonder if it does. It seems to me that there is no way for participants to authenticate each other securely. There are, though, signaling servers, but I don't think that they are capable of key ...
Enr1g's user avatar
  • 198
2 votes
3 answers
99 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 ...
flo von der uni's user avatar
2 votes
1 answer
441 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 ...
Thunderbird's user avatar
2 votes
2 answers
341 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 ...
Henrick Hellström's user avatar
2 votes
1 answer
120 views

Does having more than one HMAC provide more information to the attacker?

Suppose $N$ many messages has been sent from $A$ to $B$ in this format: $\operatorname{HMAC}(K, C(i)) \mathbin\| C(i)$. Where $C(i)$ is some cipher-text encrypted with some secure algorithm using ...
CuriousCrypto's user avatar
2 votes
1 answer
678 views

Why is DH key exchange still useful, if a public key certificate is used?

EDIT: According to Gilles's comments and fgrieu's answer below, I would like to summarize what I have learned, and what's still needs explanation: DHKE is necessary for forward secrecy even when PKI ...
xrfang's user avatar
  • 159