# Tag Info

5

PSS is harder to implement because it uses randomness -- randomness is hard on many embedded systems like smart cards. The most proclaimed advantage of PSS is that it has a "security proof" with, apparently, a rather tight reduction (see this page for some references). Security proofs are not an easy subject; the proof for OAEP (the encryption padding which ...

3

This is all about the question of risk assessment. Are you willing to risk all devices together so that if one key is compromised, they all have to be returned? What is the cost of one return, 100 returns, or 100,000 returns? What is the expense of issuing a master key? Of issuing ten master keys? Of issuing a thousand? Do you have an estimate for how ...

2

The answer is either "no" or "it depends". Generally speaking, RSA-PSS is more robust, in the sense that you don't have to take as many extra precautions in order to use it securely. RSA-PKCS#1-v1.5 is OTOH more widely supported by pre-exisiting software, but you sometimes have to patch the way it is used in order to prevent exploits. For instance, if you ...

2

RFC 5958 and RFC5959 seems to be the latest standard for storing encrypted private keys. It obsoletes RFC 5208, also known as PKCS#8. My understanding is that AES is one of the many encryption algorithms supported by RFC 5958. The GNU Keyring File Format is a another standard for a file format that stores private keys using AES-128. The Gnome Keyring ...

2

This page gives details of a successful extraction of a 3DES key from an IBM 4758 (FIPS 140-1 Level 4): http://www.cl.cam.ac.uk/~rnc1/descrack/. In summary, it required 20 mins of access to the device, 2 days of (offline) cracking time, and about $1000 in equipment. Not sure if this quite answers the question you were asking in that it relies on ... 2 FIPS 140-2 Security Level 2 does not require any form of security measure to prevent extraction of secrets. It simply requires tamper evidence, that is, it should be possible to notice that such attack took place by looking (for instance) at some seal on the device or at a log file. To answer your question, extracting a secret may therefore take 0 seconds ... 2 There is no general way to compute the "cryptoperiod". Usually, the algorithm should specify how often you need to change keys, to achieve a desired level of security against cryptanalysis attacks. For instance, AES in CBC mode has some weaknesses once you encrypt anywhere close to$2^{64}$blocks with the same key, so you should change the key long before ... 1 Multi-prime RSA (also known as RSA-MP) is supported by PKCS#1v2. This standard supports a public key$(n,e)$where the modulus$n$is the product of$u≥2$distinct odd primes:$n=\prod_{i=1}^u{r_i}$, with$1<e<n$and$\gcd(r_i-1,e)=1$(implying$e$odd). The private exponent$d$is such that$1<d<n\$, and ...

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