Authentication is successfully validating that an entity you are communicating with is actually who they claim to be. The entity typically demonstrates who they are by showing they possess a secret that only they could know.

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Authenticate ephemeral key exchange

At the moment I'm designing a crytosystem for a VPN server. One of the requirements is Perfect Forward Secrecy, but I'n not sure how to implement authentication on the ephemeral key exchange. If both ...
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1answer
91 views

Value of S and r in Fiat-Shamir Protocol

In the book Cryptography and Network Security by Forouzan,in chapter 14, Fiat-Shamir protocol, its mentioned that two large prime numbers p and q are chosen and kept secret. However n=p*q is made ...
5
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1answer
145 views

Fast 128-bit MAC with second preimage resistance?

I have an application that needs a fast 128-bit MAC to guarantee message authenticity in a protocol. I would like to reuse this MAC value as a binding identifier, so that even those who know the key ...
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2answers
142 views

Definition of authenticity

I came across various definitions of what authenticity means in cryptography. I would like to know which one is correct. The first definition - the one I always used - is the following: Data ...
3
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1answer
110 views

Where is SRP-Z from?

The Stanford license for SRP says: Broader use of the SRP authentication technology, such as variants incorporating the use of an explicit server secret (SRP-Z), may require a license; Yet ...
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1answer
85 views

MAC tag size in AES CCM, when using CTR + CBC-MAC (not CBC MAC only)

Assuming that AES CCM is used with respect of the NONCE unicity // the key life cycle, I wonder about the need of using the highest size for CBC-MAC authentication tag if CTR mode encrypts both ...
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1answer
1k views

Security of authenticated encryption modes GCM & CCM

I have two questions for Clarification for AE mode choice criteria GCM : it appears to be actually the most popular and widely used AE mode of operation. however it is also well-known to be highly ...
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1answer
98 views

Inverse public-key encryption

I'm in the need of an inverse public-key encryption method where you encrypt with the private key and decrypt with the public key. In other words an asymetric encryption where you can't generate the ...
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1answer
44 views

Authenticating with a document

Hope you're having a nice day. I need to implement an authentication system between a "document" (it's not exactly a document, but an object without any computing capacity, only able to store ...
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1answer
49 views

TLS Handshake : Server authentication or only Server ‘s Certificate authentication?

I have some difficulty understanding the way in which the Server is really authenticated by Client in TLS handshake (in case of using RSA key exchange). When Client receives Server ‘s Certificate and ...
2
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1answer
59 views

Can we use the authentication tag as Nonce / IV for the next message?

Let's assume we're in some scenario requiring transfer of large amounts of data. This means we can only use AES-GCM chunk-for-chunk as its maximal size is restricted to a few GiBs. This means we have ...
2
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2answers
98 views

Client login without sending a password

I would love to have a system where the password is never send in plaintext (even with TLS) to authenticate a user. I've come up with this protocol, but I'd rather use something proven. Registration: ...
5
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4answers
4k 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 ...
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1answer
123 views

public key cryptography and authentication for cross-platform network application

I'm developing network based application for control and telemetry on Linux based embedded system. I'm using ZMQ network library and Google Protocol Buffers serialization library for communication ...
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4answers
282 views

Why aren't zero-knowledge proofs used for authentication in practice?

I read on Wikipedia that zero-knowledge proofs are not used for authentication in practice. Instead (I think) the server is entrusted with seeing a password in plaintext form, which it should then add ...
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0answers
65 views

Understanding a faulty Needam-Schroeder protocol

Give this mutual-authentication protocol (along with the attack) in which Alice wants to communicate with Bob, I can't understand how the attack works. A chooses $N$ (nonce) and sends to C (trusted ...
3
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1answer
102 views

UKS attack on KEA protocol

I'm trying to understand the UKS attack on KEA protocol. This is described in this paper: Security Analysis of KEA Authenticated Key Exchange Protocol So to summarize: KEA protocol: UKS ...
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0answers
208 views

What is the original SKID3 protocol?

While searching for a mutual authentication protocol I often stumbled upon SKID3. However I encountered different variations of it. The basic structure is the following: (1) A --> B: rA (2) B --> ...
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2answers
78 views

Is there a signature scheme for the Cramer-Shoup cryptosystem?

I have a project that I have to use cryptosystem and signature scheme for it. I've read about Cramer-Shoup cryptosystem and I want to use it since it is more secure the ElGamal cryptosystem, but, I ...
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1answer
122 views

How can I generate a good password from a SHA512 hash?

I have to change local administrator passwords on machines. I don't want to store password in a database. I have to generate a password that I can find later to connect to the machine again. So I ...
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1answer
56 views

Unconditional authentication

I have a few questions regarding universal-hash functions: Is there a way universal hash functions can be used to provide unconditional authentication in the way the OTP provides unconditional ...
2
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1answer
42 views

N users must approve a request

I have a locked-down production system that we'd like to process specific requests, picked-up (poll) from a less-secure location. For security and "go slow, this is production" reasons, a request ...
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0answers
74 views

How far is public-key crypto involved in “banking world”? [closed]

I would like to know how public key cryptography is used in the banking world. I am not looking for big details, but for example: Are banking card embedding a private key used for signing ...
2
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2answers
288 views

ECDH anonymous key exchange to avoid PKI

I want to use TLS to encrypt the communication between peers in a P2P network. Each peer has a well known 256bit peer identifier (the public key of a 256bit elliptic curve keypair). Both peers need ...
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2answers
85 views
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1answer
95 views

Parallel authentication of encrypted data. What AE type to choose?

I've got a system with a slow data transfer channel. Transferring a message through several channels does increase the transfer speed significatnly. AES-CBC+HMAC is good except that verifying the MAC ...
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1answer
107 views

What is a man-in-the-middle attack (for instance in Diffie-Hellman)?

I'm new to cryptography and I just started learning about the Diffie-Hellman key agreement. I read that this system is vulnerable to a man-in-the-middle attack when used alone. What kind of attack is ...
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1answer
366 views

Suggestion : CRC vs SHA1

I need some suggestions about the use of the CRC in my application. I need to be sure about the BIOS run by the CPU. I have a FPGA between the BIOS flash and the CPU that sniff every read performed by ...
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3answers
380 views

Key derivation of public key without knowledge of private key

I'm looking for a convenient way to share a set of public keys across multiple services, while preserving privacy by preventing these services from tying the identity of these public key sets together ...
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1answer
77 views

How to select parameters based on some condition

I am implementing a protocol for authentication where parameters need to be selected with $gcd(\mu,\phi)=1$ where $\phi=(p−1)(q−1)$. What is the best way to select the parameters while implementing
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35 views

Establish authentication

I have designed a basic authentication scheme where two nodes will mutually authenticate that other holds a shared secret. I have very limited RAM/ROM (its on uC) and bandwidth. Here it goes: ...
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1answer
55 views

Security of MSS

I have started reading about the Merkle Signature Scheme. I am a little confused about why it is believed to be secure against quantum attacks, couldn't the hash function be attacked? What would make ...
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2answers
300 views

Is the HMAC construction really neccessary for a fixed length message?

The HMAC Construction is defined as: Hash( (Key XOR opad) || Hash((Key XOR ipad) || Message) ) This was designed because a simpler construction such as: ...
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2answers
42 views

Securely start a client server connection without ssl/tls [closed]

NOTE: Pardon my ignorance of encryption, I learned about these concepts today Going to rephrase this question, but I think I already have fine answers provided. I need to have a block of data ...
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1answer
86 views

On countermeasures for replay attacks. Does this one require plaint text password storage?

I was reading this wiki section on the countermeasures against replay attacks and it basically suggests that: If Bob wants to confirm Alice's identity he can send a one-time token (I think it should ...
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1answer
403 views

Trying to understand the use of ECC in TLS certificates

I was looking the certificate of this website: https://www.cloudflare.com that has an ECC based certification. I'm just curious to know if is possible to understand which elliptic curve is used and ...
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126 views

My attempt of combining socialist millionaire and Diffie-Hellman. Is it any good?

I've come up with an algorithm to solve the socialist millionaire problem, but I'm not sure if the algorithm is secure. I wasn't able to find any flaw in it, but it seems too simple to be secure, so ...
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2answers
93 views

Secure Channel - Encryption and Decryption Keys For A Message

I'm currently reading Cryptography Engineering and in Chapter 7, the topic of secure channel is discussed. The channel described is using CTR for encryption. Below I include images with pseudo-code ...
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2answers
290 views

Why does TLS do Authenticate-then-Encrypt instead of Encrypt-then-Authenticate?

Encrypt-then-Authenticate (EtA) seems to generally be considered the better option, compared to Authenticate-then-Encrypt (AtE) (see this Crypto.SE question, for example). The people writing the RFC ...
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1answer
36 views

HTTPS and plaintext authentication

I have client connecting a server over HTTPS to send and retrieve data. The client always connects through HTTPS The certificate is known to the client beforehand (hard coded into the software) The ...
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1answer
76 views

What should I think about these unique certificate serial numbers [closed]

I was looking at the serial numbers of the certificates for www.google.com and wordpress.com. Wordpress was listed by openssl as: 04:0B:D4:F8:25:88:C5 This serial is listed as the serial for both ...
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1answer
49 views

Could this alternative hash based MAC construction be as, or even more secure than an HMAC?

Begin hashing (Key||Message) Encrypt the hash state (or some part of it, such as the first 128 or 256 bits), with the key. Add the encrypted hash state to the ...
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1answer
215 views

Generate a list of valid ASCII codes

I have read many pages about encryption but I am really stuck on this. For access control to a building I want to print a 10 character ASCII code on a ticket (as a barcode). The barcode reader ...
2
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1answer
136 views

Authenticate a short message with redundant encryption instead of using a MAC?

I have a short message that’s exactly 128 bits of length. The message serves as a time-limited authorization token for a database. It contains a permission profile ID (64 bits) and an issue timestamp ...
2
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0answers
47 views

Proposed unidirectional authentication scheme

I've been looking around for a way to authenticate a client to the server and deliver a message, but in a unidirectional fashion - that is, the client sends messages to the server, but the server ...
5
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1answer
385 views

The difference between MAC algorithms and what to use

I've been looking into message authentication codes and found several ways to create integrity for a message. I know of the following algorithms: HMAC, this can use any cryptograhpic hash function ...
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1answer
185 views

Where is the authentication tag stored in file encrypted using AES-GCM?

So I am using cryptopp to encrypt a file in a project and I am using AES-GCM. I have a 256bit key and a 128bit ivec and a 128bit tag that I use to encrypt files. However, I want to know where the ...
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1answer
69 views

Which one these alternatives using authentication and encryption will solve this multiple-user database problem?

Which one these alternatives using authentication and encryption will solve this multiple-user database problem ? I'm trying to understand the field of cryptography, so I've started reading a ...
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1answer
51 views

Is authentication length always a subset of encryption length?

Do in all the use cases, if I have to encrypt and authenticate, encrypt-then-authenticate or authenticate-then-encrypt, like in IPSEC, SSL or SSH or others, if I were to do these operations to a ...
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33 views

Does it make sense to have multiple values of authentication and cipher offsets while encrypting a packet?

Consider a packet with N segments. cofsset(cipher offset - from where one must cipher) lies in arbitrary Segment "A". aoffset (authentication offset - from where one must authenticate) lies in ...