In cryptanalysis, what does it mean to break a cipher?

Breaking a cipher in the context of cryptanalysis refers to the ability to find a method to decrypt a message without access to the key, and ideally, doing so in a more efficient manner than simply trying all possible keys (brute force). This process involves analyzing the weaknesses or patterns in the cipher to exploit them, enabling the cryptanalyst to recover the plaintext message quicker than random guessing would allow.

The focus here is on efficiency; discovering a feasible method to compromise the security of the cipher without relying on exhaustive key searches illustrates a depth of understanding of the encryption method and its vulnerabilities. Successful cryptanalysis demonstrates the practical application of mathematical and logical techniques that can undermine the security framework of the cipher.

Other choices do not align with the definition of breaking a cipher. For instance, completely destroying the cipher data refers to data loss rather than decryption. Creating stronger encryption algorithms pertains to developing security measures rather than breaking existing ones. Thus, the best understanding of breaking a cipher centers on identifying alternative, more efficient decryption methods beyond brute force techniques.