Elliptic Curve Digital Signature Algorithm (ECDSA) Definition

What is ECDSA?

The Elliptic Curve Digital Signature Algorithm (ECDSA) is a cryptographic algorithm that uses elliptic curve cryptography (ECC) for generating digital signatures. This offers greater efficiency than integer-based algorithms, such as RSA, while offering the same level of security.

How Does ECDSA Work?

ECDSA is a digital signature algorithm, which is a form of asymmetric or public key cryptography. This means that each user has a public and private key. Public keys can be used to encrypt messages to that user and validate digital signatures, while private keys are used to generate digital signatures and decrypt messages.

A digital signature algorithm such as ECDSA also includes a hash algorithm. The process of generating a digital signature includes the following steps:

1. Message Digest: The digital signature algorithm will use a hash function to generate a message digest or hashed version. This has a fixed length, and — due to hash function collision resistance — it is infeasible to find two messages with the same digest (for a secure hash algorithm).
2. Signature Generation: The digital signature algorithm will actually be generated for the message digest, not the message itself. This involves “encrypting” the digest with the user’s private key so it can be “decrypted” with the corresponding public key.

After performing these steps, the signer has a digital signature for the message. They would send this signature to the intended recipient alongside the corresponding message.

Once the recipient receives this message, they’ll take the following steps to verify the signature:

1. Message Digest: Using the same hash algorithm as the sender, the recipient will generate a digest of the message. This should exactly match the digest contained within the digital signature.
2. Signature Extraction: With the user’s public key, the recipient can “decrypt” the digital signature to extract the hash generated by the sender.
3. Digest Comparison: The recipient compares the hash they generated with the one extracted from the digital signature. If they match, the message is authentic and hasn’t been tampered with.

Advantages of ECDSA

ECDSA is a popular digital signature algorithm. Some applications include authenticating data, blockchain technology, and secure communications.

ECDSA is more popular than many alternatives due to its use of ECC rather than integer-based cryptography. ECC provides the same level of security as integer-based cryptography with a smaller secret key. As a result, it requires less storage space and runs much more quickly and efficiently than comparable algorithms.

ECDSA Security

The main security assumption of ECDSA and similar algorithms is that the public key used for signature verification actually belongs to the alleged sender. If not, an attacker could substitute their own public key and generate valid signatures while masquerading as the alleged sender. Public key infrastructure (PKI) and similar systems are used to distribute and verify the authenticity of public keys.

Conclusion

ECDSA is a widely used digital signature algorithm that leverages elliptic curves for greater efficiency and security. With ECDSA — and similar digital signature algorithms — it’s possible to verify that data was generated by the alleged sender and not tampered with in transit.