Mercurial > dropbear
annotate libtomcrypt/notes/tech0005.txt @ 817:a625f9e135a4
Constant time memcmp for the hmac and password crypt
author | Matt Johnston <matt@ucc.asn.au> |
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date | Thu, 03 Oct 2013 22:25:30 +0800 |
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1 Tech Note 0005 |
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2 Minimizing Code Space |
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3 Tom St Denis |
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4 |
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5 Introduction |
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6 ------------ |
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8 Tweaking... |
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10 You can disable whole classes of algorithms on the command line with the LTC_NO_* defines. From there you can manually turn on what you want to enable. |
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11 |
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12 The following build with GCC 3.4.4 on an AMD64 box gets you AES, CTR mode, SHA-256, HMAC, Yarrow, full RSA PKCS #1, PKCS #5 and ASN.1 DER in |
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13 roughly 40KB of code (49KB on the ARMv4) (both excluding the math library). |
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15 CFLAGS="-DLTC_NO_CIPHERS -DLTC_NO_HASHES -DLTC_NO_PRNGS -DLTC_NO_MACS -DLTC_NO_MODES -DLTC_NO_PK -DRIJNDAEL -DLTC_CTR_MODE -DSHA256 \ |
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16 -DLTC_HMAC -DYARROW -DMRSA -DMPI -DTFM_DESC -DARGTYPE=3 -Os -DLTC_SMALL_CODE -fomit-frame-pointer" make IGNORE_SPEED=1 |
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17 |
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18 Obviously this won't get you performance but if you need to pack a crypto lib in a device with limited means it's more than enough... |
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19 |
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20 Neato eh? |