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Security professional with many years of experience with the practical application of cryptographic algorithms and protocols. I'm helping with the design of protocols and API's within international standardization bodies. Lead developer of a common criteria certified product. Over 30 years of general experience with computers.


Jan
17
comment How to implement HMAC SHA-256
Remember: for almost all crypto algorithms there are test vectors available online: see my question here for possible locations (that was about block ciphers, but the same thing goes for HMAC's etc). One day does not sound too bad, actually, you can easily try forever if you don't know the exact binary input to a cryptographic algorithm.
Jan
17
comment How to implement HMAC SHA-256
The online encoder is correct if you interpret the key 256'h603deb1015ca71be2b73aef0857d77811f352c073b6108d72d9810a30914dff4 as ASCII. However, if I input your message without quotation marks I get 292ed0240964c62dc685ebf028801fdb4e5895a1f908c7c824dd53a993fc4e66 (and the same on Java).
Jan
17
revised How to implement HMAC SHA-256
added 1 character in body
Jan
17
revised How to implement HMAC SHA-256
added 306 characters in body
Jan
17
comment How to implement HMAC SHA-256
OK, so they perform character encoding for the key value as well, while you are specifying hex characters. This may mean that you are using hex decoded bytes instead. And their sample key is in hex; brilliantly stupid - don't use code from random sites!
Jan
17
comment How to implement HMAC SHA-256
What online calculator, could you point it out to me? What encoding does it use? PS don't prefix 256'h to your code and use backticks (`) around your values to show them as code, like this: d48ea6df738d5791c9ca0d7ece4f0e76006bd01f3a2b917d7e1316515d1ac951.
Jan
17
answered How to implement HMAC SHA-256
Jan
17
asked Performing HMAC with random key before MAC comparison
Jan
17
comment RSA signing security
Warning: also dangerous in situations where commands are completed quickly; i.e. within a millisecond or so. Computer clocks often don't have more precision.
Jan
17
comment RSA signing security
@RickyDemer I think those are separate issues. If a large enough, cryptographically secure, random nonce is used then neither should be a problem though.
Jan
17
revised RSA signing security
edited body
Jan
16
comment Can AES in CCM or GCM counter mode interoperate with AES in “plain” counter mode (CTR)?
This answer is missing the part where you have to advance the counter with 1 before decryption with AES-CTR (for GCM anyway).
Jan
16
comment Can AES in CCM or GCM counter mode interoperate with AES in “plain” counter mode (CTR)?
@ReinierTorenbeek That would be weird. If GCM is available then CTR should be available. One rather weird method would be to recreate the key stream by encrypting all zero's and then XOR that with the received ciphertext.
Jan
16
comment Help converting sha256 to 32-bit stream
I guess that should be $\lceil\frac{32}{3}\rceil\cdot 4 = 44$ as, for 3 bytes, base64 only uses 4 characters. But that doesn't matter for this result. Thanks for the additional info @HennoBrandsma
Jan
16
comment Exploration of Blum Micali Security By Seed Size
I guess most PRNG's are "mathematically based". 20 digits is about (20 /3 * 10) ~ 64 bits. That's quite a lot so it is little wonder if it is enough to pass most tests. However, any PRNG will have some internal state. You can have a 1024 bit seed, but that won't translate to 1024 bits of security. OK, that's for the generic remarks, now I've got to read Blum Micali :)
Jan
16
revised Help converting sha256 to 32-bit stream
added 197 characters in body
Jan
16
answered Help converting sha256 to 32-bit stream
Jan
16
comment The perfect way of using IV in CTR mode
Glad it helped. If you think this has helped you enough, please accept the answer (by clicking the V-sign) or indicate what's missing.
Jan
13
comment Automated testing of cipher security for import/export compliance
Nowadays import restrictions are arguably more of an issue, especially for repressive governments.
Jan
13
comment The perfect way of using IV in CTR mode
I'm wondering how many HSM's implement CTR mode and leak the KCV value. There may be quite a lot of them...