This paper investigates ownership types in a concurrent setting using the Join calculus as the model of processes. Ownership types have the effect of statically preventing certain communication, and can block the accidental or malicious leakage of secrets. Intuitively, a channel defines a boundary and forbids access to its inside from outer channels, thus preserving the secrecy of the inner names from malicious outsiders. Secrecy is also preserved in the context of an untyped opponent.