hash.Reset() hash.Write(label) lHash := hash.Sum(nil) firstByteIsZero := constanttime.ByteEq(em[0], 0) seed := em[1 : hash.Size()+1] db := em[hash.Size()+1:] mgf1XOR(seed, mgfHash, db) mgf1XOR(db, mgfHash, seed) lHash2 := db[0:hash.Size()] // We have to validate the plaintext in constant time in order to avoid // attacks like: J. Manger. A Chosen Ciphertext Attack on RSA Optimal // Asymmetric Encryption Padding (OAEP) as Standardized in PKCS #1 // v2.0. In J. Kilian, editor, Advances in Cryptology. lHash2Good...