Fix typos
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@ -26,7 +26,7 @@ BLS12-381 is a pairing-friendly elliptic curve construction from the [BLS family
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* q = z<sup>4</sup> - z<sup>2</sup> + 1
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* = `0x73eda753299d7d483339d80809a1d80553bda402fffe5bfeffffffff00000001`
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... yielding two **source groups** G<sub>1</sub> and G<sub>2</sub>, each of 255-bit prime order `q`, such that an efficiently computable non-degenerate bilinear pairing function `e` exists into a third **target group** G<sub>T</sub>. Specifically, G<sub>1</sub> is the `q`-order subgroup of E(F<sub>p</sub>) : y<sup>2</sup> = x<sup>3</sup> + 4 and G<sub>2</sub> is the `q`-order subgroup of E'(F<sub>p<sup>2</sup></sub>) : y<sup>2</sup> = x<sup>3</sup> + 4(u + 1) where the extention field F<sub>p<sup>2</sup></sub> is defined as F<sub>p</sub>(u) / (u<sup>2</sup> + 1).
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... yielding two **source groups** G<sub>1</sub> and G<sub>2</sub>, each of 255-bit prime order `q`, such that an efficiently computable non-degenerate bilinear pairing function `e` exists into a third **target group** G<sub>T</sub>. Specifically, G<sub>1</sub> is the `q`-order subgroup of E(F<sub>p</sub>) : y<sup>2</sup> = x<sup>3</sup> + 4 and G<sub>2</sub> is the `q`-order subgroup of E'(F<sub>p<sup>2</sup></sub>) : y<sup>2</sup> = x<sup>3</sup> + 4(u + 1) where the extension field F<sub>p<sup>2</sup></sub> is defined as F<sub>p</sub>(u) / (u<sup>2</sup> + 1).
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BLS12-381 is chosen so that `z` has small Hamming weight (to improve pairing performance) and also so that `GF(q)` has a large 2<sup>32</sup> primitive root of unity for performing radix-2 fast Fourier transforms for efficient multi-point evaluation and interpolation. It is also chosen so that it exists in a particularly efficient and rigid subfamily of BLS12 curves.
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@ -34,7 +34,7 @@ BLS12-381 is chosen so that `z` has small Hamming weight (to improve pairing per
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Pairing-friendly elliptic curve constructions are (necessarily) less secure than conventional elliptic curves due to their small "embedding degree". Given a small enough embedding degree, the pairing function itself would allow for a break in DLP hardness if it projected into a weak target group, as weaknesses in this target group are immediately translated into weaknesses in the source group.
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In order to achieve reasonable security without an unreasonably expensive pairing function, a careful choice of embedding degree, base field characteristic and prime subgroup order must be made. BLS12-381 uses an embedding degree of 12 to ensure fast pairing performance but a choice of a 381-bit base field characteristic to yeild a 255-bit subgroup order (for protection against [Pollard's rho algorithm](https://en.wikipedia.org/wiki/Pollard%27s_rho_algorithm)) while reaching close to a 128-bit security level.
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In order to achieve reasonable security without an unreasonably expensive pairing function, a careful choice of embedding degree, base field characteristic and prime subgroup order must be made. BLS12-381 uses an embedding degree of 12 to ensure fast pairing performance but a choice of a 381-bit base field characteristic to yield a 255-bit subgroup order (for protection against [Pollard's rho algorithm](https://en.wikipedia.org/wiki/Pollard%27s_rho_algorithm)) while reaching close to a 128-bit security level.
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There are [known optimizations](https://ellipticnews.wordpress.com/2016/05/02/kim-barbulescu-variant-of-the-number-field-sieve-to-compute-discrete-logarithms-in-finite-fields/) of the [Number Field Sieve algorithm](https://en.wikipedia.org/wiki/General_number_field_sieve) which could be used to weaken DLP security in the target group by taking advantage of its structure, as it is a multiplicative subgroup of a low-degree extension field. However, these attacks require an (as of yet unknown) efficient algorithm for scanning a large space of polynomials. Even if the attack were practical it would only reduce security to roughly 117 to 120 bits. (This contrasts with 254-bit BN curves which usually have less than 100 bits of security in the same situation.)
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@ -256,7 +256,7 @@ impl Scalar {
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//
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// and computing their sum in the field. It remains to see that arbitrary 256-bit
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// numbers can be placed into Montgomery form safely using the reduction. The
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// reduction works so long as the product is less than R=2^256 multipled by
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// reduction works so long as the product is less than R=2^256 multiplied by
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// the modulus. This holds because for any `c` smaller than the modulus, we have
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// that (2^256 - 1)*c is an acceptable product for the reduction. Therefore, the
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// reduction always works so long as `c` is in the field; in this case it is either the
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