133 lines
4.4 KiB
Plaintext
133 lines
4.4 KiB
Plaintext
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#
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# For a description of the syntax of this configuration file,
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# see scripts/config/Kconfig-language.txt
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#
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menu "BigInt Options"
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depends on !CONFIG_SSL_SKELETON_MODE
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choice
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prompt "Reduction Algorithm"
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default CONFIG_BIGINT_BARRETT
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config CONFIG_BIGINT_CLASSICAL
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bool "Classical"
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help
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Classical uses standard division. It has no limitations and is
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theoretically the slowest due to the divisions used. For this particular
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implementation it is surprisingly quite fast.
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config CONFIG_BIGINT_MONTGOMERY
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bool "Montgomery"
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help
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Montgomery uses simple addition and multiplication to achieve its
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performance. In this implementation it is slower than classical,
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and it has the limitation that 0 <= x, y < m, and so is not used
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when CRT is active.
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This option will not be normally selected.
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config CONFIG_BIGINT_BARRETT
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bool "Barrett"
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help
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Barrett performs expensive precomputation before reduction and partial
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multiplies for computational speed. It can't be used with some of the
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calculations when CRT is used, and so defaults to classical when this
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occurs.
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It is about 40% faster than Classical/Montgomery with the expense of
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about 2kB, and so this option is normally selected.
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endchoice
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config CONFIG_BIGINT_CRT
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bool "Chinese Remainder Theorem (CRT)"
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default y
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help
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Allow the Chinese Remainder Theorem (CRT) to be used.
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Uses a number of extra coefficients from the private key to improve the
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performance of a decryption. This feature is one of the most
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significant performance improvements (it reduces a decryption time by
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over 3 times).
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This option should be selected.
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config CONFIG_BIGINT_KARATSUBA
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bool "Karatsuba Multiplication"
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default n
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help
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Allow Karasuba multiplication to be used.
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Uses 3 multiplications (plus a number of additions/subtractions)
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instead of 4. Multiplications are O(N^2) but addition/subtraction
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is O(N) hence for large numbers is beneficial. For this project, the
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effect was only useful for 4096 bit keys. As these aren't likely to
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be used, the feature is disabled by default.
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It costs about 2kB to enable it.
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config MUL_KARATSUBA_THRESH
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int "Karatsuba Multiplication Theshold"
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default 20
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depends on CONFIG_BIGINT_KARATSUBA
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help
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The minimum number of components needed before Karasuba muliplication
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is used.
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This is very dependent on the speed/implementation of bi_add()/
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bi_subtract(). There is a bit of trial and error here and will be
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at a different point for different architectures.
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config SQU_KARATSUBA_THRESH
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int "Karatsuba Square Threshold"
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default 40
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depends on CONFIG_BIGINT_KARATSUBA && CONFIG_BIGINT_SQUARE
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help
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The minimum number of components needed before Karatsuba squaring
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is used.
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This is very dependent on the speed/implementation of bi_add()/
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bi_subtract(). There is a bit of trial and error here and will be
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at a different point for different architectures.
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config CONFIG_BIGINT_SLIDING_WINDOW
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bool "Sliding Window Exponentiation"
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default y
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help
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Allow Sliding-Window Exponentiation to be used.
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Potentially processes more than 1 bit at a time when doing
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exponentiation. The sliding-window technique reduces the number of
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precomputations compared to other precomputed techniques.
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It results in a considerable performance improvement with it enabled
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(it halves the decryption time) and so should be selected.
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config CONFIG_BIGINT_SQUARE
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bool "Square Algorithm"
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default y
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help
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Allow squaring to be used instead of a multiplication.
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Squaring is theoretically 50% faster than a standard multiply
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(but is actually about 25% faster).
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It gives a 20% speed improvement and so should be selected.
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config CONFIG_BIGINT_CHECK_ON
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bool "BigInt Integrity Checking"
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default n if !CONFIG_DEBUG
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default y if CONFIG_DEBUG
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help
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This is used when developing bigint algorithms. It performs a sanity
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check on all operations at the expense of speed.
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This option is only selected when developing and should normally be
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turned off.
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endmenu
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