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Tech Note 0005
Minimizing Code Space
Tom St Denis
Introduction
------------
Tweaking...
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.
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
roughly 40KB of code (49KB on the ARMv4) (both excluding the math library).
CFLAGS="-DLTC_NO_CIPHERS -DLTC_NO_HASHES -DLTC_NO_PRNGS -DLTC_NO_MACS -DLTC_NO_MODES -DLTC_NO_PK -DLTC_RIJNDAEL -DLTC_CTR_MODE -DSHA256 \
-DLTC_HMAC -DYARROW -DMRSA -DMPI -DTFM_DESC -DARGTYPE=3 -Os -DLTC_SMALL_CODE -fomit-frame-pointer" make IGNORE_SPEED=1
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...
Neato eh?
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