Brute force code cracking question.

[Guv]

Just started reading a novel (Digital Fortress by Dan Brown) which is about NSA, the code cracking agency.

A character in the novel claims that brute force methods can always crack a code based on an encryption key. This claim does not seem close to being correct to me.

It seems to me that a key 100 bits long requires 2¹⁰⁰ tries to be certain of finding the key, although you could be lucky and find it in ten tries. On average, it would take 2⁵⁰ tries.

A key several thousand bits long would take many life times of the universe if you could make millions of tries per nanosecond.

Are there any code cracking gurus here with an opinion?