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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Possibility of Man-in-the-Middle on X3DH

I'm reading about the security of the Signal protocol (used in WhatsApp) and in particular, the X3DH part used to establish authentication, all papers seem to gloss over Man in the Middle attacks. Is ...
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Diffie-Hellman man-in-the-middle attack

Diffie-Hellman Key Exchange Basic Protocol: Let G be a cyclic group of order $n$ and generator $g$. Alice chooses $a \in \{0,\ldots,n-1\}$ and Bob chooses $b \in \{0,\ldots,n-1\}$. ...
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If two hosts are using a transparent IP level authentication and encryption, is their communication subject to both MITM or replay attacks?

Encryption process for any outgoing packet to the specified "remote IP": -original payload P is encrypted (the bytes after the IP header) using RC4 with the preestablished key ...
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Can Alice encrypt a message to Bob without hiding anything from Eve? [duplicate]

I know that if Alice and Bob both have secret-public key pairs, they can use RSA for example. If we remove the possibility that Alice can know anything which Eve doesn't (ie Alice's secret key), is ...
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Triple Diffie-Hellman and MITM

While reading about Triple Diffie-Hellman, I was wondering how it can prevent MITM if the server decides to spoof key sets. For example, Alice and Bob are connected using a server. Alice ----- ...
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attacks and defenses on multi party Diffie-Hellman protocol

I tried to create a 4 partied Diffie-Hellman implementation for 4 people using its cyclic group property. However, I am not sure regarding those 2 issues, and would appreciate if you could elaborate ...
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Server stored, encypted messaging app

For my personal research, I have to create a messaging app, but security is only important part of application, security from MITM (man in the middle attack), at device end, and at server level. (note:...
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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 ...
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How does DHE-RSA work and why is PFS guaranteed?

How does it work and why is forward secrecy guaranteed? I understood that it is not susceptible to a man-in-the-middle attack by using certificates in the beginning.
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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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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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Prevent a Man-In-The-Middle attack whilst transmitting a PSK for first time

I'm developing a network where two parties that want to join both compute ephemeral ECC keys for a key exchange, to create an encrypted connection. I plan to authenticate these keys by signing them ...
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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.
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How is STS more secure than regular DH

I'm trying to understand the STS protocol (using the wikipedia page as source), but I don't see how this protocol is any more secure than DH regarding man in the middle attacks. If Alice and Bob don'...
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66 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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Entity authentication protocol by encryption

I'm not a cryptography expert, so excuse me if the question seems very trivial. I need to know if this protocol is secure against a MiTM attacks and ensure a safe entity authentication method. We ...
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Is this man in middle atack possible in quantum cryptography? [duplicate]

Lets consider there is channel between Alice and Bob, sequered with quantum cryptography. To put it simple, Alice is left, Bob is right and the quantum states are 'up' ~ U and 'down' ~ D. Alice ...
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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 ...
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Needham–Schroeder fix by adding opponent's identity to the first message

Recap: Needham–Schroeder is as follows: $A \rightarrow B : \{A, N_a\}_{pk_B}$ $B \rightarrow A : \{N_a, N_b\}_{pk_A}$ $A \rightarrow B : \{N_b\}_{pk_B}$ Then, there is a MITM attack by Lowe ...
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How to decrypt plain text x using man in the middle attack

Suppose Alice want to share a plain text $x = 5$ to Bob; using RSA, DHKE, and El-Gamal. My question is if Man-in-the-middle attack is applied then weather oscar can compute/decrypt plain text in all ...
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Security of the Needham-Schroeder public key protocol after a minor adjustment

I'm preparing for a computer security exam by going through some past paper questions. And I came across this particular one that I could not answer: We have the Needham Schroeder Public Key Protocol:...
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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, ...
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Public key on Server Key Exchange Generation vs Public key on Server's Certificate

To understand the distinction between TLS 1.2 and TLS 1.3. I am stuck in the past understanding for TLS and the current reference I am studying: As I know certificate goes with owner's public key, ...
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Detect MITM with hashed session-key — Is my protocol secure?

I have the following setup: An app ("client") wants to communicate securely with a device I created ("server"). The client has the public key of the server (and a hashed password) preinstalled. I use ...
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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 ...
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How is it possible for a VPN connection to be created through the ISP?

I will be theoretical here. Let's say you want to create a VPN connection with some VPN provider. You have to agree on some key to encrypt the data. how can you get the key without your ISP knowing it?...
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Authentication and integrity

I was trying to solve this problem: Sometimes Alice needs to send a file to Bob, guaranteeing her identity and the file integrity (no confidentiality required); the two parties are sharing a secret w ...
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485 views

MD5 hash functions to prove integrity of a download

It doesn't take a lot of time on the crypto StackExchange to realise the sentiment around MD5 hash functions is poor. My questions are: If it's such a bad idea to make use of MD5 hash functions why ...
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What can I do, if my SRP password verifier was stolen?

I've got a system that works like this: ...
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144 views

ECDH vs MITM ablity to change content

We all know how DH is great, and ECDH is much greater, but only in case of Eve spying on public keys, so how can ECDH defeat the ablity of "Eve" to change the public keys between Bob and Alice with ...
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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 ...
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Is it impossible to have a decentralized service using email addresses as login?

Let's say we have a decentralized service S distributed on a network of 1000 nodes/servers. Is it possible to have a registration/sign up scheme using email address ...
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Organizational Internal Man In The Middle Scenario

Question. I'm a software developer. I design and write secured systems for my customer. My customer recently downward directed that all traffic to/from my server be routed through a new appliance. I ...
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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 ...
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223 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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Is it Possible to Generate a Duplicate DH Session Key from 2 Pairs of DH Keys?

This might sound pointless at first, but I want to know if it's computationally feasible to generate the same resulting session key in 2 different DH key exchanges. The purpose would be for a man-in-...
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179 views

Negotiate a secure connection without certificates?

I would like to have a simple experience for a user for setting up a secure connection between two computers against a MITM attack. Something like the following: A number (possibly base64) appears ...
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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, ...
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251 views

Securing an end-to-end encrypted cloud based address book

I am analyzing an existing end-to-end encrypted, cloud based service (e.g. email, file storage or chat) which also has a public cloud based address book (for managing contacts) so that users of the ...
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564 views

MITM defense in Diffie-Hellman protocol

Let's consider that Alice and Bob both know a shared secret $secret$ and don't know each other DH public keys. They want to authenticate each other and their keys using only $secret$. Let's also ...
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HMAC usage in hybrid encryption scheme [duplicate]

Consider the following hybrid encryption scheme (B3||4 is for concatenated IV and AES-CBC encrypted message): ------------------------------------------------------...
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666 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 ...
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277 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 ...
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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 ...
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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 ...
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783 views

how to get secret keys in xor?

1) a = b ⊕ s1 2) b = a ⊕ s1 3) b ⊕ s2 = c Is there a way to find s1 and s2 if we know many different values of a and c? 4) a1 = b1 ⊕ s1 5) a1 ⊕ s1 ⊕ s2 = c1 I think it is possible if we analysis ...
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Using a single key pair for man-in-the-middle attack on Diffie-Hellman

Assume that a man-in-the-middle attack on the Diffie-Hellman key exchange protocol is possible, for which the adversary generates two public–private key pairs for the attack. Could the same attack be ...
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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}...
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831 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 ...
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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 ...