Which of the following best describes the level of risk associated with using proprietary crypto algorithms? 

Proprietary cryptographic algorithms are required by law to use shorter key lengths in the United States, so the risk is high. 

Proprietary algorithms have not been subjected to public scrutiny, so they have been checked less throughly for vulnerabilities. 

Proprietary algorithms are less likely be vulnerable than algorithms that have been publicly disclosed because of enhanced secrecy of the algorithm. 

Proprietary algorithms are not known to generally be any more or less vulnerable than publicly scrutinized algorithms.