# What is the limit of plaintext required to break the Vigenère encryption?

A theoretical question about the Vigenère cipher:

1. Without any knowledge about the key (not even it's length) can we tell how much known or chosen plaintext is needed for the adversary to completely recover the key?
2. What about if we know the key length? (I assume that we'll need plaintext with the same length of the key).
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