Invalid Curve Attack Affecting openpgp package, versions <4.2.1

openpgp is a JavaScript implementation of the OpenPGP protocol.

Affected versions of this package are vulnerable to Invalid Curve Attack. It allows an attacker, who is already able provide forged messages and gain feedback about whether decryption of these messages succeeded, to conduct an invalid curve attack in order to gain the victim's ECDH private key.

Elliptic Curve Cryptography (ECC) is used in key exchange protocolsdigital signatures, or for pseudo-random number generators. An elliptic curve in cryptography is a set of points over a finite field satisfying the following equation: y^2 = x^3 + ax + b. On the elliptic curve, a single operation can be executed: point addition.

Elliptic curve Diffie–Hellman (ECDH) is an anonymous key exchange protocol that allows two parties (say, between a client and server) to establish a shared secret over an insecure channel.

An Invalid Curve Attack occurs when a client forces the server to compute a common secret using a point outside of the defined curve. The server may disclose information, allowing a skilled attacker to calculate the secret key.

• GitHub Commit
• GitHub PR
• GitHub Release
• Research Paper (BSI Germany)
• Sec-Consult Blog Post