  Wireless communication is susceptible to adversarial eavesdropping due to the
broadcast nature of the wireless medium. In this paper it is shown how
eavesdropping can be alleviated by exploiting the superposition property of the
wireless medium. A wiretap channel with a helping interferer (WT-HI), in which
a transmitter sends a confidential message to its intended receiver in the
presence of a passive eavesdropper, and with the help of an independent
interferer, is considered. The interferer, which does not know the confidential
message, helps in ensuring the secrecy of the message by sending independent
signals. An achievable secrecy rate for the WT-HI is given. The results show
that interference can be exploited to assist secrecy in wireless
communications. An important example of the Gaussian case, in which the
interferer has a better channel to the intended receiver than to the
eavesdropper, is considered. In this situation, the interferer can send a
(random) codeword at a rate that ensures that it can be decoded and subtracted
from the received signal by the intended receiver but cannot be decoded by the
eavesdropper. Hence, only the eavesdropper is interfered with and the secrecy
level of the confidential message is increased.
