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Passive RFID tags harvest their operating energy from an interrogating reader, but constant energy shortfalls severely limit their computational and storage capabilities. We propose Cryptographic Computational Continuation Passing (CCCP), a mechanism that amplifies programmable passive RFID tagsΓÇÖ capabilities by exploiting an often overlooked, plentiful resource: low-power radio communication. While radio communication is more energy intensive than flash memory writes in many embedded devices, we show that the reverse is true for passive RFID tags. A tag can use CCCP to checkpoint its computational state to an untrusted reader using less energy than an equivalent flash write, thereby allowing it to devote a greater share of its energy to computation. Security is the major challenge in such remote checkpointing. Using scant and fleeting energy, a tag must enforce confidentiality, authenticity, integrity, and data freshness while communicating with potentially untrustworthy infrastructure. Our contribution synthesizes well known cryptographic and low-power techniques with a novel flash memory storage strategy, resulting in a secure remote storage facility for an emerging class of devices. Our evaluation of CCCP consists of energy measurements of a prototype implementation on the batteryless, MSP430-based WISP platform. Our experiments show thatΓÇödespite cryptographic overheadΓÇö remote checkpointing consumes less energy than checkpointing to flash for data sizes above roughly 64 bytes. CCCP enables secure and flexible remote storage that would otherwise outstrip batteryless RFID tagsΓÇÖ resources. This work will appear at USENIX Security 2009. Paper: http://www.cs.umass.edu/~negin/files/salajegheh-CCCP-usenix09.pdf