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A fast stream cipher using add-rotate-xor operations designed for software efficiency.
DESCRIPTION
Salsa20 is a family of ARX-based stream ciphers created by Daniel J. Bernstein for high performance in software. It generates keystream from a key, nonce, and counter, encrypting by XOR with plaintext. Variants trade rounds for speed versus security margins. Salsa20 influenced ChaCha20, widely standardized in TLS and SSH. It is valued for simplicity, speed, and resistance to common attacks under recommended parameters.
ALTERNATIVE DEFINITIONS
Daniel J. Bernstein
Salsa20 is a family of 256-bit stream ciphers designed for high-speed software encryption.
Inventor’s page emphasizing speed and 256-bit design.
IACR ePrint
The Salsa20 family uses add-rotate-xor operations to efficiently produce pseudorandom keystream from a key and nonce.
Technical report detailing ARX construction.
eSTREAM (ECRYPT)
Salsa20 is a software-oriented stream cipher submitted to the eSTREAM project, with recommended variants.
Notes evaluation under the eSTREAM initiative.
RELATED TERMS
Stream Cipher Nonce Keystream Poly1305 Cryptanalysis Randomness
COMPETING TERMS
KNOWLEDGE AREAS
TARGET AUDIENCE
Security Architect Cybersecurity Engineer Software Developer Chief Information Security Officer
EXTERNAL SOURCES
- Wikipedia - Salsa20
- Daniel J. Bernstein - Original specification and discussion
- IACR ePrint - Technical report on Salsa20
- ECRYPT eSTREAM - Project evaluation summary
TOP QUESTIONS
What is Salsa20?
It’s a software-efficient stream cipher using add-rotate-xor operations to generate keystream for encryption.
Category: Definition
How does Salsa20 compare to ChaCha20?
ChaCha20 refines Salsa20’s diffusion and rotation constants, improving security margins and adoption in standards.
Category: Comparison
What are Salsa20’s inputs?
A secret key, nonce, and block counter; it outputs a pseudorandom keystream XORed with plaintext.
Category: Concepts
Is Salsa20 standardized?
Salsa20 itself is not an IETF RFC standard, but is widely documented and evaluated; ChaCha20 is standardized.
Category: Standards
Where is Salsa20 used?
In some software libraries and legacy systems; modern protocols more often use ChaCha20-Poly1305.
Category: Usage
What are common implementation risks?
Nonce reuse, weak key management, and side-channel leaks can compromise security.
Category: Risk
What performance characteristics define Salsa20?
High speed on general-purpose CPUs due to ARX operations and simple structure.
Category: Performance
What is a competing term for Salsa20?
ChaCha20 or AES-CTR serve similar roles with different design trade-offs.
Category: Alternatives
Who created Salsa20?
Daniel J. Bernstein designed Salsa20 as part of stream cipher research.
Category: Origin