Supreme Court of India laid the explanation for the definition of conspiracy as prescribed u/s  120A IPC (and punishment u/s 120B IPC).

From Para 32,

32. Therefore, in order to constitute a conspiracy, meeting of mind of two or more persons to do an illegal act or an act by illegal means is a must. In
other words, it is sine qua non for invoking the plea of conspiracy against the accused. However, it is not necessary that all the conspirators must  know each and every detail of the conspiracy, which is being hatched and nor it is necessary to prove their active part/role in such meeting.

Citations: 2018 SCC OnLine SC 1865

Indiankanoon.org link: https://indiankanoon.org/doc/31194569/

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