RSA Security 5.2.2 manual Security Considerations, Handling Private Keys, Elliptic Curve Standards

Security Considerations

already in place, or where a hardware developer wants to be able to provide a platform that supports both RSA and elliptic curve encryption.

For the even characteristic finite field, F2m, there is also a choice of representation. For these fields, elements can be represented using a polynomial basis, a normal basis, or some other basis. For some values of m, elements can also be represented in an optimal normal basis, which is generally more efficient than an ordinary normal basis. In order for systems that use different bases to communicate, they need to convert from one representation to another. Each representation has advantages and disadvantages, including efficiency and potential patent coverage, so in current elliptic curve standards the choice is typically left to the implementation.

Elliptic Curve Standards

The elliptic curve algorithms in Crypto-C are compliant with the ANSI X9.62 standard. The elliptic curve implementation is also based on the IEEE P1363 draft standard.

Security Considerations

This section discusses security considerations when using public-key cryptography. The following issues are discussed: handling private keys, temporary buffers, pseudo-random numbers and seed generation, choosing passwords, initialization vectors and salts, DES weak keys, stream ciphers, timing attacks and blinding, and choosing key sizes.

Handling Private Keys

In public-key cryptography, only the owner of a private key can create a digital signature or open digital envelopes. However, if someone other than the owner is able to obtain the private key, the security fails. To ensure that no one other than the owner has access to a private key, it should be stored encrypted, generally with a password- based encryption method. An application will decrypt the private key when it is needed. Always overwrite the memory that held a private key with zeroes or random bytes immediately after the key has performed its function.

Operating systems will frequently use the hard disk space as virtual memory, so an unencrypted private key may, through no intention of a user, end up on a hard disk. Hence, for key buffers, an application should use the operating system’s mechanisms

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