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Consistently describe Ed25519 as a 255-bit curve

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The coordinates are over $F_{2^{255}-19}$, so by the general
definition of the bit size associated with the curve in the
specification, the value for size attribute of keys is 255.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2021-03-16 18:25:14 +01:00
parent 7e54a29bea
commit a00abc6b65
2 changed files with 3 additions and 3 deletions
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4
include/psa/crypto_values.h
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@ -586,11 +586,11 @@
/** The twisted Edwards curves Ed25519 and Ed448.
*
* These curves are suitable for EdDSA (#PSA_ALG_PURE_EDDSA for both curves,
* #PSA_ALG_ED25519PH for the 256-bit curve,
* #PSA_ALG_ED25519PH for the 255-bit curve,
* #PSA_ALG_ED448PH for the 448-bit curve).
*
* This family comprises the following twisted Edwards curves:
* - 256-bit: Edwards25519, the twisted Edwards curve birationally equivalent
* - 255-bit: Edwards25519, the twisted Edwards curve birationally equivalent
* to Curve25519.
* Bernstein et al., _Twisted Edwards curves_, Africacrypt 2008.
* - 448-bit: Edwards448, the twisted Edwards curve birationally equivalent

2
scripts/mbedtls_dev/crypto_knowledge.py
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@ -78,7 +78,7 @@ class KeyType:
'PSA_ECC_FAMILY_SECT_R2': (163,),
'PSA_ECC_FAMILY_BRAINPOOL_P_R1': (160, 192, 224, 256, 320, 384, 512),
'PSA_ECC_FAMILY_MONTGOMERY': (255, 448),
'PSA_ECC_FAMILY_TWISTED_EDWARDS': (256, 448),
'PSA_ECC_FAMILY_TWISTED_EDWARDS': (255, 448),
}
KEY_TYPE_SIZES = {
'PSA_KEY_TYPE_AES': (128, 192, 256), # exhaustive