Granted Patent B2

US 7,549,147 · App. 10/414,314 · Granted Jun 16, 2009

Abstract

Claims (25)

1. A method for protecting software, source code for the software having a first directive marking an encryption beginning point and a second directive marking an encryption end point, the method comprising the steps of:

processing the source code to identify a block of code between the first and second directives;

compiling the source code to produce a binary file;

generating a random string and establishing a mechanism that allows the software to obtain a valid key from a data flow expected to be received by the software in a manner that the valid key is neither stored within the software, nor located in a remote storage, but instead is obtained from the data flow,

wherein the step of establishing the mechanism further comprises the steps of:

encrypting the random string with the valid key to obtain a first encrypted value;

encrypting a portion of the binary file corresponding to the block of code with the valid key to obtain a second encrypted value; and

replacing the portion of the binary file corresponding to the block of code with the second encrypted value and code that can decrypt the second encrypted value during execution of the software,

accepting a binary string believed to be the valid key;

encrypting the random string with the binary string believed to be the valid key to obtain a third encrypted value;

comparing the third encrypted value to the first encrypted value; and

decrypting the second encrypted value with the binary string believed to be the valid key if the first encrypted value equals the third encrypted value.

2. The method of claim 1 , further comprising the step of storing line number information for the block, wherein the step of encrypting the portion of the binary file is based on the stored line number information.

3. The method of claim 1 , further comprising the step of decrypting the encrypted portion of the binary file during execution of the binary file based on the valid key obtained during execution of the binary file.

4. The method of claim 3 , further comprising the steps of:

accepting a trigger value;

generating a hash of the trigger value;

comparing the hash of the trigger value to a hash of the valid key; and

outputting the valid key if the hash of the trigger value equals the hash of the valid key.

5. The method of claim 3 , further comprising the steps of:

accepting a sequence of trigger values;

encrypting the random string using the sequence of trigger values as keys to obtain a first sequence of encrypted values;

comparing the first sequence of encrypted values to a second sequence of encrypted values obtained by encrypting the random string with a sequence of secret sub-keys; and

outputting a secret key if each member of the first sequence of encrypted values equals each respective member of the second sequence of encrypted values,

wherein the secret key is equal to an exclusive OR of the sequence of secret sub-keys.

Assignments (16)