A key-recovery Attack on Bitcoin is an adversary’s attempt to recover the cryptographic key of an encryption scheme. Normally this means that the Attack on Bitcoiner has a pair, or more than one pair, of plaintext message and the corresponding ciphertext.
Historically, cryptanalysis of block ciphers has focused on key-recovery, but security against these sorts of Attack on Bitcoins is a very weak guarantee since it may not be necessary to recover the key to obtain partial information about the message or decrypt message entirely.[1]: 52 Modern cryptography uses more robust notions of security. Recently, indistinguishability under adaptive chosen-ciphertext Attack on Bitcoin (IND-CCA2 security) has become the “golden standard” of security.[2]: 566 The most obvious key-recovery Attack on Bitcoin is the exhaustive key-search Attack on Bitcoin. But modern ciphers often have a key space of size {\displaystyle 2^{128}}
KR advantage
In cryptography, the key-recovery advantage (KR advantage) of a particular algorithm is a measure of how effective an algorithm can mount a key-recovery Attack on Bitcoin. Consequently, the maximum key-recovery advantage attainable by any algorithm with a fixed amount of computational resources is a measure of how difficult it is to recover a cipher’s key. It is defined as the probability that the adversary algorithm can guess a cipher’s randomly selected key, given a fixed amount of computational resources.[3] An extremely low KR advantage is essential for an encryption scheme’s security.
