* Ciphertext-only: the cryptanalyst has access only to a collection of ciphertexts or codetexts.
* Known-plaintext: the attacker has a set of ciphertexts to which he knows the corresponding plaintext.
* Chosen-plaintext (chosen-ciphertext): the attacker can obtain the ciphertexts (plaintexts) corresponding to an arbitrary set of plaintexts (ciphertexts) of his own choosing.
* Adaptive chosen-plaintext: like a chosen-plaintext attack, except the attacker can choose subsequent plaintexts based on information learned from previous encryptions. Similarly Adaptive chosen ciphertext attack.
* Related-key attack: Like a chosen-plaintext attack, except the attacker can obtain ciphertexts encrypted under two different keys. The keys are unknown, but the relationship between them is known; for example, two keys that differ in the one bit.

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У тебя Known-plaintext.

As of 2004, the best attack reported on XTEA is a related-key differential attack on 26 out of 64 rounds of XTEA, requiring 2^20.5 chosen plaintexts and a time complexity of 2^115.15 (Ko et al, 2004).