simplesshd/dropbear/libtomcrypt/notes/tech0005.txt

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?
stock dropbear-2014.66 source tree 2014-12-10 21:56:49 +00:00			`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).`

stock dropbear-2019.78 source tree 2019-06-09 20:44:26 +00:00			`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 \`
stock dropbear-2014.66 source tree 2014-12-10 21:56:49 +00:00			`-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?`