ECC Tool - Elliptic Curve Encryption & Signatures

ECC is a public-key cryptosystem built on elliptic curves of the form y² = x³ + ax + b, whose security relies on the intractability of the Elliptic Curve Discrete Logarithm Problem (ECDLP). At equivalent security strength, ECC keys (e.g., 256-bit) are drastically shorter than RSA keys (~3072-bit).

ECC supports three major operations: ECIES public-key encryption / decryption (for confidential data transfer), ECDSA / EdDSA signing & verification (for authentication and tamper-proofing), and ECDH key agreement (enabling two parties to derive a shared secret without prior key exchange).

This tool performs key generation, encryption, decryption, signing, and verification for P-256/P-384/P-521, secp256k1, Ed25519, and Curve25519/X25519 — all locally in your browser. It is a handy aid when debugging ECC-based APIs or validating ciphertext/signature formats.

Several mainstream ECC curves are in use, each optimized for different scenarios. The curves supported by this tool include:

• P-256 / P-384 / P-521: NIST-standardized curves, natively supported by the Web Crypto API — suitable for encryption, signing, and ECDH.
• secp256k1: the Koblitz curve used by Bitcoin and Ethereum, known for efficient signing and verification.
• Ed25519: an Edwards curve purpose-built for EdDSA signatures, featuring high speed, simple implementation, and side-channel resistance.
• Curve25519 / X25519: Montgomery curves purpose-built for ECDH key agreement, and used as the default by TLS 1.3.

Mode selection guide: use ECIES for encrypted data transfer; use EdDSA / ECDSA for authentication; use ECDH for session key negotiation. Hex and Base64 input/output formats are interchangeable to facilitate integration with different systems.

Please keep in mind: ECC public-key encryption only protects data confidentiality during transfer — it does not replace transport-layer security. Production deployments should pair it with SHA-256/SHA-512 hashing, AES symmetric encryption, and a TLS/HTTPS channel.

All key generation, encryption/decryption, signing, and ECDH negotiation performed by this tool happen locally in your browser. Nothing is uploaded to a server, and nothing is persisted to localStorage.

Additional recommendations:

• When working with production private keys, operate in a private/incognito window or offline, and clear inputs when done.
• In production environments, ECC private keys must be stored in encrypted form (e.g., via PKCS#8 + passphrase, or in an HSM).
• For signing/verification, align on the signature encoding format (DER (ASN.1) or R|S concatenation) to avoid verification failures.
• For encryption/decryption, ensure both parties use the same curve, the same key encoding format (Hex or Base64), and a consistent input/output format convention.