1. A method in a proxy server that is coupled with an origin server, comprising: receiving, from a requesting device, a request for a web page of the origin server; retrieving the requested web page; determining that the retrieved web page includes a web form that includes a set of one or more form attribute values for obfuscation; modifying the retrieved web page including obfuscating the set of form attribute values into a corresponding set of one more obfuscated form attribute values, wherein obfuscating the set of form attribute values includes performing the following: determining a first set of one or more values of a set of one or more characteristics of the requesting device, deriving a first symmetric key from at least the first set of values, and encrypting the set of form attribute values using the first symmetric key; transmitting the modified web page to the requesting device, wherein the set of form attribute values in their original form is not included in the modified web page; receiving, from the requesting device, form data for the set of obfuscated form attribute values; deobfuscating the set of obfuscated form attribute values thereby revealing the set of form attribute values, wherein deobfuscating the set of obfuscated form attribute values includes performing the following: determining a second set of one or more values of the set of characteristics of the requesting device, deriving a second symmetric key from at least the second set of values, and decrypting the set of obfuscated form attribute values using the second symmetric key, wherein the second symmetric key and the first symmetric key are equivalent; and responsive to the deobfuscation, transmitting the form data with the set of form attribute values to the origin server.