Poly1305-AES is a cryptographic message authentication code (MAC) written by Daniel J. Bernstein. It can be used to verify the data integrity and the authenticity of a message.

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Why is Poly1305 popular given its 'sudden death' properties?

ECDSA has the undesirable property that if a key pair reuses a nonce in a signing operation, the cryptosystem experiences catastrophic failure in the form of private key leakage. I've heard this ...
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129 views

Are poly1305 authenticators distinguishable from random data?

Assume Alice authenticates a message $M$ with nonce $N$ and secret key $K$, creating authenticator $A$. She then sends $A$ across the network. The Poly1305 paper does not seem to specify whether it ...
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1answer
363 views

Can Poly1305 be used with block ciphers running in CTR mode?

Is the use of Poly1305 limited to stream ciphers? (note, I'm not talking about Poly1305-AES )? Can it be used with block ciphers running in CTR mode? If so, what other considerations/limitations are ...
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331 views

Nonce encryption with Poly1305-Chacha20

I have seen that a couple of companies (like Google, Apple HomeKit) are adding "ChaCha20-Poly1305" as an encryption option. Poly1305 requires algorithm to encrypt the nonce. The Poly1305-AES ...
6
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1answer
709 views

Why does NaCl's crypto_secretbox for xsalsa20-poly1305 require the first 32 bytes to be zero?

The NaCl web site says this is a requirement of the API, but its seems more than just an API issue. It means the first 32 bytes of the first salsa20 block are effectively ignored. I didn't see ...
6
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1answer
363 views

How does NaCL Poly1305 implementation do modular multiplication?

The NaCL ref implementation of Poly1305 performs modular multiplication to calculate a polynomial $\mod 2^{130} - 5$ using the following modular multiplication ...
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1k views

ChaCha cipher + Poly1305

The Poly1305-AES paper summarizes the MAC as $$ \mathrm{Poly1305}(m, \mathrm{AES}_k(n)) = {H_r(m) + \mathrm{AES}_k(n)} \mod 2^{128} $$ Can I presume that $+$ here is just meant as a form of 16-byte ...
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1answer
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Do Carter–Wegman MACs allow key reuse if the MAC tag is kept secret?

Poly1305 (and GHASH) are secure authenticators, but only for one use. Thus, nonce reuse in Poly1305-AES, ChaCha20-Poly1305, and AES-GCM all reveal the authentication key. However, my understanding ...
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1answer
199 views

Can Poly1305-AES be used with AES-256?

I'm reading through Bernstein's The Poly1305-AES message-authentication code. The MAC is predicated on 16-byte block ciphers like AES and produces 16-byte authentication tags. However, Bernstein does ...
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2answers
184 views

What is the function of the secret key “r” in Poly1305?

Poly1305-AES uses two per-connection keys $k$ (for AES) and $r$ (for Poly1305's compression function) and a per-message nonce n to execute. I've read the original paper on the implementation, and I ...
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1answer
59 views

Advantages of HS1-SIV over ChaCha20-Poly1305-SIV?

What advantages does HS1-SIV have over ChaCha20-Poly1305-SIV? I know that both use the ChaCha stream cipher, but I am trying to understand why HS1-Hash is a better MAC. Edit: To hide the Poly1305 ...
2
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1answer
124 views

chacha20-poly1305 padding and length encoding

The AEAD construction for chacha20-poly1305 described in the IETF proposal encodes message lengths into the text that is to be hashed. The newer proposal goes further and pads associated data and ...
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1answer
318 views

How does Poly1305 in the NaCl library calculate a MAC?

I've been reading about Poly1305 as implemented in the NaCl library, more specifically I've been referring to this Java implementation of NaCl. My understanding of XSalsa20Poly1305 (in this ...
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1answer
90 views

What happens if a nonce is reused in ChaCha20-Poly1305?

In ChaCha20-Poly1305, I know that reusing a nonce loses confidentiality and integrity for all messages encrypted with the (key, nonce) pair. However, is security affected for those messages encrypted ...
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0answers
34 views

Is XSalsa20-Poly1305-SIV a reasonable choice for nonce-misuse-resistant authenticated encryption?

Consider XSalsa20-Poly1305-SIV. This is obtained by: computing a MAC $t_{secret}$ of the plaintext from the key and nonce, as in ChaCha20-Poly1305 except that the plaintext, not the ciphertext, is ...
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0answers
39 views

Can an attacker recover the key if a Poly1305 collision is known?

Suppose that messages $m_1$ and $m_2 \neq m_1$, both known to the attacker, are both MAC'd through Poly1305 with the same key. By chance, these two messages hash to the same value. The attacker ...
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0answers
23 views

Are there any holes in my stateless encryption protocol?

I want to create a reasonably secure protocol to allow a bunch of machines within a datacenter to securely communicate to one another. Specifically as a kind of tunnel. I want to avoid building up ...
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0answers
36 views

Poly1305 vs VMAC: is VMAC much better for long messages?

VMAC seems to me much more secure than Poly1305 on long messages (the security of the latter decreases linearly with increasing message length). Is this of practical relevance?