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Questions tagged [authenticated-encryption]

Combination of encryption and authentication in a way that ensures confidentiality and integrity.

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XTS mode of operation and authentication

I'm wondering if XTS is used (Random Access is needed) what the best solution for authentication is. If I wouldn't need random access, I would take AES-GCM or AES-CBC-HMAC but random access is a must. ...
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Understanding ChaCha20-Poly1305 AEAD

In the AEAD scheme described in https://tools.ietf.org/html/rfc7539#section-2.8.1, the aad and cyphertext are padded to be a multiple of 16 bytes in length. Why is this necessary? Does it provide any ...
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AEAD using AES-CBC and MAC: how to order the input to the MAC

I'm writing code to provide an AEAD utility. It uses AES-256-CBC for encryption and SHA-512(key+data) truncated to 256 bits as the MAC. ...
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135 views

Do AEADs also authenticate the nonce?

I'd like to include an authenticated timestamp in my messages. I'm wondering if I can save a little space by putting the timestamp in the nonce. Concrete example: Let's say I'm using XChaCha20-...
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1answer
155 views

Symetric key encryption is not Authentication?

Is there any way to show CCA-secure symmetric-key encryption does not have to be an authenticated encryption? I know you can create a setup that isn't authentication, but how will you go about it?
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Disadvantage of the using a counter within plain text for encrypting with AES256 and authentication?

What if we use a counter within the plain text and then encrypt the plain text with aes 256 to encrypt & authenticate? For example: encryptAES(32bit_counter+plain_text_of_96bit); or encryptAES(...
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2answers
64 views

Using a hash of data instead of the full raw data for authenticated data in AES-GCM

I am serialising JSON objects, and would like to encrypt some of the values. I plan to do this with AES-GCM. I would also like to ensure the integrity of the overall object. The requirements are ...
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1answer
31 views

Verion of crypto_box() which doesn't allow the sender to decrypt previously sent messages

Libsodium's crypto_box() family of functions allow the sender to send messages using its public/private keypair knowing the receiver's public key, and allow the ...
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124 views

Are SSH key-pairs an example of a zero knowledge proof?

Quoting from source, authentication using SSH key pairs goes something like this: 1) The client begins by sending an ID for the key pair it would like to authenticate with to the server. 2) ...
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1answer
25 views

Are Authenticated Encryption ciphersuites supported in legacy TLS versions older than TLS 1.2?

I have read in a paper that Authenticated Encryption (by this I mean those that support GCM mode or ChaCha20 ciphers) are not supported in versions older than TLS 1.2? I could not confirm this as ...
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171 views

Why does TLS 1.3 support two CCM variants?

One of the important improvements introduced in TLS 1.3 is the pruning of the many previously available cipher suites to only five secure options (for symmetric ciphers), that are each supposed to ...
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3answers
401 views

In what cases might PRESENT be implemented as encryption-only?

In the paper, under section 4.1 Goals and environment of use we read: In applications that demand the most efficient use of space, the block cipher will often only be implemented as encryption-only. ...
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1answer
87 views

Is Strong MAC stronger than existential unforgeability?

Especially in the context of Encrypt-then-Authenticate.
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4answers
114 views

JWT Login Security

I am new to security and I am wondering if JWT is secure enough. From what I have read online the flow goes like this: Clients log in by sending their credentials to the identity provider. The ...
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Patent Status & Usability of AE Modes [closed]

Post Structure: Sources Cited Question & Details Before You Answer Useful Info From Comments Sources Cited: https://blog.cryptographyengineering.com/2012/05/19/how-to-choose-authenticated-...
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1answer
42 views

A feasible approach for AEAD on an ethernet link?

The setup is shortly this: There are two custom switches (think of an FPGA for example), both are handling 10-100 Gb/s orders of traffic from their outside facing interfaces. This is normal traffic. ...
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CPA-secure private-key encryption scheme that is unforgeable but is not CCA-secure

This is exercise with 4.26 in Katz and Lindell's introduction to cryptography 2nd ed. The question is: Show a CPA-secure private-key encryption scheme that is unforgeable but is not CCA-secure. ...
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1answer
64 views

Is there any way to track if a ciphertext has been decypted?

Just like the case of a box that has been sealed. We can detect if the box has been opened or not by looking at the seal. Is there any way in cryptography or any encryption scheme that allows this to ...
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53 views

Authenticated encryption vs end-end encryption

I am kind of new to crypto. can someone highlight the differences between authenticated encryption and End-to-End encryption
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122 views

Reason for 3 rounds ChaCha in ChaCha20Poly1305@openssh

OpenSSH uses a slightly different ChaCha20Poly1305 AEAD construct then the one proposed by A. Langley and others for TLS. The TLS version The openSSH version (and here) The openSSH version uses two ...
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GCM mode of operation with long-term keys

Cross-post: https://cstheory.stackexchange.com/q/41435/873 Regarding GCM, NIST specifies the following: The total number of invocations of the authenticated encryption function shall not exceed $2^...
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1answer
67 views

Re-using information from the first factor for the second factor

Is it safe to re-use my username and password as information for the 2nd-factor? For instance: the first factor is the username and password; the second factor is $H(H(username) \oplus H(password \| ...
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149 views

Is an AEAD the recommended method to add encryption + HMAC to a protocol?

Assuming you are dealing with a competent developer/team, and you are advising on adding security to their protocol. Also for the time being lets not worry about the key establishment and validating ...
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42 views

Encryption / Decryption method secure

I was wondering whether this encryption / decryption flow is very solid / secure. I encrypt the data using AES CBC 256 bit with an static IV. When the user logs in with his Firebase account (first ...
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XEX vs EME mode of operation

Two of the CAESAR finalists use XEX and EME mode of operations (COLM uses EME, OCB uses XEX). I did literature to summarize the main advantages / disadvantages but I could not find much. My question ...
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1answer
116 views

Is it safe to use unauthenticated AES CBC when encrypting random bytes?

I am studying an application with an AES crypto implementation that works that like the following: PBKDF2 is used with X iterations and SHA-256 to generate a 256-bit "master key" from a user-provided ...
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2answers
93 views

Why is release of unverified plaintext so Bad?

Lately I came across of release of unverified plaintext. I was told that this is a bad thing, but I don't really get why. Isn't unverified plaintext released just nonsense? How can this be attacked in ...
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44 views

What is the difference between verifying the hash value (MAC) and security provided by authenticated encryption?

I read this post Difference between MAC and Authenticated Encryption? but I'm still confusing the difference. Seems like MAC can guarantee both integrity and authenticity (tbh I dont know the ...
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3answers
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Secure MAC and secure encryption schemes combined to form insecure Authenticated Encryption?

I'm reading up on Authenticated Encryption and can't really wrap my head around how a generally secure MAC and a generally secure encryption scheme can be combined into an insecure AE scheme, such as ...
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1answer
153 views

Is transporting a salt, IV, ciphertext and HMAC in an encrypted token an acceptable practice?

I’m porting over some crypto code from Mcrypt (deprecated) to OpenSSL. I’m following a process that a former employee implemented, which is as follows: Create a random salt for use in a PBKDF2 key ...
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1answer
60 views

Propagating CBC insecure Authenticated Encryption

why is Propagating CBC (PCBC) insecure for authenticated encryption? I received the hint that I should feed a message of length $n$ and a message of length $n-1$ to it, but I don't really get what the ...
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2answers
823 views

Are TLS 1.2 AES-CBC and AES-GCM Authenticated Encryption ciphersuites?

In the answer of the following post: Why was AES CBC removed in TLS 1.3?, I quote the following from the chosen answer: After the Lucky13 attack (a timing oracle caused by MAC-then-encrypt), it ...
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What happens in the MonkeyWrap-Algorithm of KetjeV2 if the input is a single block?

I am currently implementing KetjeV2 in VHDL. I have a question concerning the MonkeyWrap-Algorithm that is used in KetjeV2. The function $wrap(A, B, l)$ is supposed to work as shown below, where $A$ ...
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1answer
129 views

AES-PMAC-SIV AE algorithm

AES-SIV is a very robust and safe algorithm but performance isn't great. AES-PMAC-SIV, should provide a great parallelization, increasing performance and ensuring the same robustness. Indications of ...
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2answers
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Authentication scheme to protect against fake devices

I want two embedded devices (call them master and slave) to communicate with each other. For intellectual property protection, the master must reject fake slave devices (the other way around is a pre ...
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1answer
41 views

Distinct MAC and Key for AEAD?

I am implementing some of the algorithms in RFC 7518 and I noticed that AES_CBC_HMAC_SHA2 contains the following paragraph: The secondary keys MAC_KEY and ENC_KEY are generated from the ...
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135 views

How to implement security - authenticity/confidentiality/integrity for 6/14 bits radio messages?

I just took over two radio systems (using 433Mhz) - one communicates with 6 bit messages, one with 14 bit messages. Both have a lots of transmitters and one receiver (and, yes bits not bytes). For ...
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1answer
90 views

6 Byte for HMAC in wireless system secure?

A wireless system has 8 byte payload and 6 byte for message authentication. Scheme: ...
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0answers
49 views

Rationale behind IETF-ChaChaPoly's padding during MAC computation [duplicate]

RFC 7539 (Section 2.8) specifies a ChaCha20/Poly1305 based AEAD cipher scheme; pseudocode: ...
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1answer
62 views

Should I include the ciphertext length in an AAD when using Chacha20+Poly1205 AEAD?

I want to construct a time-limited authorization token using ChaCha20 and Poly1305 as defined by RFC7539. I chose the following simple layout: ...
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1answer
141 views

Security strength for encryption and authentication (wrapping) of cryptographic keys

Let $K$ and $M$ be AES secret keys. The purpose is to wrap $K$ using $M$ to allow $K$ to be used at a later time (see, e.g. NIST SP 800-38F, section 3.1). One method to achieve this goal is to use $M$ ...
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1answer
147 views

Verifying signature of plaintext using encrypted message only

I'm looking for an algorithm which allows verifying a signature of a plaintext message but while only having the encrypted message. The requirement is for Alice to send Bob a plaintext message (M) ...
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32 views

Authorizing someone to open Alice's lock when Alice's lock only has Alice's public key

I'm designing a lock and I want Alice to be able to give temporary permission to someone to open the lock. After a set amount of 'access time' that someone should not have access to open the lock ...
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1answer
64 views

Do you need to MAC an ECIES message?

Normally, when decrypting messages, you need to check if the message is authentic and integral (aka, never decrypt before checking the MAC). With ECIES, this seems to be done internally. Is it ...
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1answer
84 views

What does GHASH really do?

I try to understand the GCM-MODE used in TLS. The problem I have had is described below. 1:textbook describes how GHASH works: 2: I get some debuginfo from openssl code that contain enc_key(32 bytes)...
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37 views

Extending IGE to provide authentication

I was playing around with the idea of modifying infinite garble extension (IGE) mode to provide authentication in one pass. I was also doing some Google searches today to see if there were any ...
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1answer
70 views

Robust cryptosystem for files/chunks protection?

I'm not a cryptographic expert by far but I do understand that when it comes to cryptography it's best to stick with established standards. I have to ensure confidentiality and integrity of a bunch ...
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1answer
75 views

Verifying integrity of large files

I'm looking for the most efficient in memory and time way to verify integrity of large files which have to be encrypted as well. Using SHA256 and other crypto hashes over the whole encrypted file? ...
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1answer
81 views

CBC-MAC 8 octet ICV compatable with 16 octet block size?

I'm trying to use DTLS in Preshared key mode for CoAP which necessitates using CipherSuite TLS_PSK_WITH_AES_128_CCM_8 I'm trying to start with the CBC-MAC but I'm not sure how to get an 8 octet ICV ...
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1answer
44 views

Authenticated encryption with forged verification key

Is it part of the (or a common) security model of symmetric authenticated encryption to prevent an adversary from exhibiting a decryption/verification key that makes a given genuine ciphertext verify, ...