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Questions tagged [poly1305]

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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Poly1305-AES vs AES-GCM

What are the advantages of Poly1305-AES over AES-GCM? Please note I am not talking about chacha20-Poly1305 that has been widely adopted, including by Google. But I would like to know pros and cons ...
user12480's user avatar
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6 votes
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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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Is Poly1305 an information-theoretically secure MAC?

I have heard some people say that the Poly1305 authenticator is a "nuclear" MAC i.e. it is information-theoretically secure. After reading the paper I see it is based on the Wegman-Carter MAC which is ...
lightspeeder's user avatar
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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 ...
edifice's user avatar
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Would it be safe to use the message hash as the IV in ChaCha?

This seemed like an option if the hash is unpredictable. It could be the hash of the message or the hash of the message + some common secret (apart from the key). The only circumstance in which the ...
alandefreitas's user avatar
4 votes
2 answers
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Why not use chacha derivatives (BLAKE, rumba) to make an [H]MAC for use with chacha? Why use poly1305?

Why not use chacha derivatives (BLAKE, rumba) to make an [H]MAC for use with chacha? Why use poly1305? This question is especially interesting considering... "The security of Poly1305[...] is very ...
Charlie's user avatar
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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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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 ...
Demi's user avatar
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3 votes
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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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1 vote
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Security level of Poly1305 and GMAC

The Libsodium docs list the AEAD forgery limits for ChaCha20Poly1305 and AES-GCM which seems like a < 128-bit security level but says that it's not a practical concern. I've seen other people say ...
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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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7 votes
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Is there an upper limit to plaintext size in XSalsa20Poly1305?

While fiddling with the NaCl implementation in Go, specifically SecretBox, a general crypto question came up after reading the documentation. Quote: Package secretbox encrypts and authenticates ...
Awn's user avatar
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6 votes
1 answer
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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 ...
Demi's user avatar
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Does ChaCha20-Poly1305 need random nonce?

RFC 7539 says: A 96-bit nonce -- different for each invocation with the same key It doesn't explicitly say whether it has to be random or not. If we use an ever incrementing counter. Would that be ...
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3 votes
1 answer
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What is meant by a 1.5 pass cipher?

In What is the advantage of AEAD ciphers? Maarten Bodewes used the term 1.5 pass cipher in his answer. What is the difference between a 1.5 pass cipher and a 2 pass cipher? And why is Poly1305 a 1.5 ...
dr_exmat's user avatar
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How does the squeeze function in the NaCl Poly1305 implementation work?

The NaCl ref implementation of the Poly1305 algorithm uses the following reduction function (which is called squeeze()): ...
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