Implicit Certificate Generation for Weak Random Number Generators
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Solution Overview
Problem
The security of public key cryptographic systems is compromised due to weaknesses in random number generators, particularly in constrained devices like cell phones and smart cards, where low entropy can lead to the exposure of private keys during public key transmission, potentially disclosing corresponding private information.
Innovation Solution
A method is introduced to mask the output of a random number generator by using a deterministic encryption scheme, such as RSA, to encrypt the public key before distribution, and employing an implicit certificate protocol to avoid direct exposure of the private key, ensuring secure key establishment between computing devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a random number generator is used to generate private keys in constrained devices, then key generation is enabled, but security is compromised due to low entropy and weak random numbers
Solution Approach 1:
A trusted party acts as an intermediary between the constrained device and the public key infrastructure. The trusted party receives the weak public key from the device, combines it with a strong random value generated by itself, and produces a strengthened public key. This intermediary process allows constrained devices to use simple RNG while maintaining security through the trusted party's intervention.
Solution Approach 2:
The patent changes the entropy parameter of the public key by combining a weak random value from the constrained device with a strong random value from the trusted party. This parameter transformation converts a low-entropy public key into a high-entropy strengthened public key, resolving the security issue without requiring the device to have better RNG capabilities.
2Productivity
If public keys are transmitted directly without masking, then communication efficiency is maintained, but private keys may be exposed due to weak random number generators
Solution Approach 1:
The trusted party serves as a mediator that receives the vulnerable public key, processes it by combining with strong randomness, and returns a strengthened public key. This intermediary processing step masks the weakness of the original public key while maintaining the efficiency of the key exchange process.
Solution Approach 2:
The trusted party performs preliminary strengthening of the public key before it is used in communication. By pre-combining the weak public key with strong random values, the system prepares a secure public key in advance, preventing private key exposure during subsequent communication operations.
3Reliability
If deterministic encryption is used to mask public keys, then security against weak RNG is improved, but computational overhead increases
Solution Approach 1:
The trusted party performs the computationally intensive deterministic encryption operation, not the constrained device. The device simply provides its weak public key and receives the strengthened version, avoiding the computational overhead while still benefiting from the security improvement.
Solution Approach 2:
The trusted party uses its own strong random number generation capability to strengthen the public key, rather than requiring the constrained device to perform complex cryptographic operations. This self-service approach by the trusted party reduces the computational burden on the device.
Data Source
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AI summary
To mitigate the effects of a weak random number generator (34) in a public key cryptosystem, a public key obtained from the random number generator (34) is encrypted using a deterministic cryptographic scheme before being made publicly available. A trusted party (14) receiving the encrypted public key can recover the public key and combine it with other information so it is not subject to direct scrutiny. In one embodiment, the trusted party (14) incorporates the public key in a certificate, such as an implicit certificate, for use by the correspondents in other communications.