Questions tagged [authenticated-encryption]

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

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1answer
52 views

Is using HMAC signature as a long-term password secure?

I'm considering implementing an authentication service without storing users' passwords/hash. I want to use a key derivation function with a corresponding username...
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865 views

Why do one-time pads not provide message authentication?

It is often said that one-time pads do not provide message authentication. But, if you and I have a one-time symmetric key, and I send you a message, and it is not complete gibberish, is that itself ...
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Which HMAC scheme more secure?

Which HMAC scheme is more secure? Or are they of the same level of security? Scheme One Compute a HMAC on the data to encrypt (cleartext/plaintext) Encrypt the data with AES_CTR_256, and append ...
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81 views

Is using the same MAC twice insecure?

I was thinking last night about whether or not a HMAC-Encrypt-HMAC would be secure if you used the same HMAC key. Here is the full recipe: Compute a HMAC on the data to encrypt, and append it to the ...
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Can I use a fixed IV with AES-GCM if I only encrypt unique plaintext values? [duplicate]

My use case guarantees that all plaintext values are unique. In this case, is it safe to use a fixed IV with AES-GCM to carry our encryption/decryption?
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Is using different public keys for different peers safer than reusing the public key, beyond forward secrecy?

In X25519 (ECDH over Curve25519) Peer A and B exchange their Public Keys ...
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82 views

AEAD (for AES128-GCM): is it necessary to add a zero-length AAD?

In an implementation of AEAD_AES_128_GCM, if the AAD is defined as a "zero-length octet sequence", is it necessary to call the encryption code that adds an AAD at all? In particular, does an OpenSSL/...
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1answer
66 views

Energy consumption by mobile or sensor node when executing xor / encryption / decryption [closed]

I try to estimate the energy consumption by a sensor node when executing an authentication algorithm witch contains operations (hashing, XOR, Encryption / decryption by public/private key, addition,......
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2answers
118 views

Any benefit to encrypting IV and MAC in a mode like AES-GCM or ChaChaPoly?

Would there be any benefit to symmetrically encrypting the IV and MAC in an AEAD mode of operation? More specifically would this prevent someone from exploiting the accidental use of a duplicate IV ...
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1answer
63 views

Decrypt authenticated cipher while still encrypting [duplicate]

Normal AES-GCM generates an authentication tag at the end of encryption. I want to decrypt it while it is still being encrypted. This would be useful to send, encrypt, receive and decrypt a large file ...
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What is the difference between an anonymous-encryption scheme and an authenticated-encryption scheme?

I was going through Indy-SDK when these two schemes were referenced. I want to know the precise differences between the two. Indy-SDK links for reference to: authenticated-encryption scheme ...
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AEAD without explicit authentication tag

I'm trying to understand the purpose of tag in AEAD. As far as I can understand, the resulting ciphertext will be slightly longer than the plaintext due to the authentication tag. Will it reduce the ...
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Plain text size limits for AES-GCM mode at 2GB with Sun JCE implementation?

The Sun JCE implementation of GCM is hard coded to refuse to encode more than 2 Gb, through the function GaloisCounterMode.checkDataLength() that returns an error message : "SunJCE provider only ...
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Robust authentication and integrity for short OTP message

Using any of the wonders of modern cryptographic technology, how is it possible to package a tweet-sized plaintext, which is to be encrypted with a proper one-time pad, to ensure its integrity and ...
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2answers
107 views

Append data to authenticated ciphertext encrypted using a stream cipher

Say we have xSalsa20 authenticated using Poly1305. If $ X $ is the ciphertext, $N$ is the nonce value, and $H$ is the authentication tag such that the final ciphertext is $ N || X || H $, then given ...
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Do AEAD algorithms and encrypt-then-MAC mitigate external decryption oracles?

I'm curious about a possible attack scenario that I'm not sure exists. If it is possible, I'd like to know if and how AEAD algorithms and encrypt-then-MAC implementations protect against it. The ...
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1answer
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Encrypting more than ~64GiB with AES-GCM - Integrity

I'm looking for solution to encrypt more than acceptable limit ~64GiB under same key with AES-GCM. I know I'm obligated to exchange nonces for each next ~64GiB chunk, but there is one thing that is ...
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3answers
241 views

Largest message size for XChaCha20-Poly1305

libsodium documentation says that XChaCha20-Poly1305 can encrypt a message of arbitrary size. However, the only specification available (still a draft) explains that under the hood the IETF version ...
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1answer
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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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2answers
79 views

Choice between appending or prepending nonces to ciphertexts

I understand that when using CTR mode it is usually secure to append or prepend the nonce to the resulting ciphertext, whether the nonce is before or after the ciphertext being unimportant. However, ...
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2answers
170 views

Where shall we use an authenticated encryption mode?

I learned from Wikipedia that authenticated encryption modes include OCB, CCM, EAX, GCM, and so on. Does this mean that when we want to use authenticated encryption we shall use these modes? But these ...
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How does the offline authentication work?

In these slides, offline and online PUF-based authentication protocols are explained in minute 16:30 and 17:30, respectively. I understand the way the online protocol works. Basically, the server ...
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1answer
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What Are Secure Limits to Truncate the Authentication Tag (Mac) for Short Messages?

I have messages with the following fixed lengths: 4 byte 8 byte 16 byte I want to encrypted them and prevent modification by appending an authentication tag using a MAC algorithm of my choosing (e.g....
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2answers
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What is the security concept in printer cartridge?

Based on this datasheet or this patent, one of the usage of PUF is printer cartridge identification and authentication. I was wondering why printer cartridge needs identification and authentication. ...
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40 views

Quick scan which data (hmac/fernet) can be decrypted with a key?

I am designing a secure vault, which stores tens of thousands of encrypted messages and authenticated with Fernet/HMAC, A user query the vault with a key, could I use some kind of index to tell if the ...
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65 views

silly possibly original AE construction

This idea is inspired by a recent question about sending 32 byte messages, encrypted, without a MAC but still achieving the equivalent protection of a MAC just by using a block cipher, extra ...
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3answers
123 views

Can I achieve data authentication with ChaCha20 without MAC?

My case is rather special. I need to send data in small chunks, each under 32bytes. ChaCha20 state is 64 bytes. Since I will be receiving data stream in chunks, id like to verify it on the fly (i.e. ...
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1answer
109 views

Cryptographic equivalent of family coat of arms

As a layman when it comes to cryptography, I have recently been asking myself if there was a cryptographic equivalent of a family code of arms. I'm thinking of something asymmetric, that is future ...
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60 views

Is it safe to use ECB mode this way, w/o duplicate blocks?

I wanna make my own "way" of encrypting separate messages. And I want it to have the least possible size overhead while being completely encrypted (hide msg counter). Here's my current idea: we ...
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1answer
151 views

Deterministic Authenticated Encryption with AES-OFB and HMAC

I have an encrypted column in a database that stores sensitive information. The existing encryption scheme is deterministic and a database index exists on the encrypted value to allow searching. I am ...
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2answers
202 views

What do NM-CPA, and NM-CCA mean?

When I've been researching authenticated encryption, the following terms keep showing up: NM-CPA NM-CCA ....without any definition as to what they mean. I've tried searching the web for their ...
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1answer
114 views

Guessing the key in AES256-GCM? [duplicate]

I assume that my case is weird but I've the following information: IV: 0x263e or 0x3e26 Auth tag: 0x25 AES256-GCM encrypted payload: 0x4eec96df534ade4c013a AES256-GCM decrypted payload: ...
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1answer
136 views

Does the AES-KW (Key Wrap Algorithm) perform authenticated encryption?

The RFC for AES-KW doesn't actually mention authentication, only integrity, where the unwrapping/decryption process should produce an identical IV of ...
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CAESAR finalists: Lightweight case (Ascon vs ACORN)

The Ascon cipher has been selected as the first choice in lightweight case and ACORN as the second. However according to Face-off between the CAESAR Lightweight Finalists: ACORN vs. Ascon paper, the ...
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1answer
78 views

Authenticated encryption and file data integrity

I've got a task to provide the integrity and an authenticated encryption for files in our application. I need an assurance if my way of thinking is correct. I can't use AES GCM, I have to stay with ...
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0answers
319 views

Key size, performance, and security tradeoffs for AES-GCM, CCM

AES can be used with 128, 192 or 256 bit keys and each one appears to have a performance vs security trade-off (What is the effect of the different AES key lengths?, What are the practical differences ...
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1answer
420 views

What is the purpose of an Authentication Tag in AEAD encryption schemes?

AEAD encryption schemes produce something referred to as an "authentication tag." What does this tag consist of, what is its purpose, and is the tag itself human-readable data such as a plaintext ...
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118 views

Does there exist a mode of operation that forces mac-then-decrypt?

Alice sends Bob a message using AES-GCM. Bob is a software developer with just enough cryptography knowledge to be dangerous. He wants to start processing data as soon as he receives it. He observes ...
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1answer
177 views

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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310 views

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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1answer
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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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1answer
238 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
167 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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1answer
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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
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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
51 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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222 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
36 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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591 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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419 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. ...