Curve25519 is a specific elliptic curve used in cryptography, designed for secure and efficient key exchange. It operates over a prime field, which enhances its security against certain types of attacks. The curve is known for its speed and simplicity, making it a popular choice for modern cryptographic protocols. One of the main applications of Curve25519 is in the Diffie-Hellman key exchange, allowing two parties to securely establish a shared secret over an insecure channel. Its design minimizes the risk of implementation errors, contributing to its widespread adoption in various security systems, including TLS and Signal.