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Update draft-irtf-cfrg-det-sigs-with-noise.md
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emanjon authored Feb 28, 2024
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10 changes: 5 additions & 5 deletions draft-irtf-cfrg-det-sigs-with-noise.md
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Expand Up @@ -482,18 +482,18 @@ For Deterministic ECDSA: In existing ECDSA deployments where side-channel and fa
~~~~~~~~~~~~~~~~~~~~~~~
d. Set:

K = HMAC_K(V || 0x00 || Z0 || 000... || int2octets(x) || 000...
K = HMAC_K(V || 0x00 || Zd || 000... || int2octets(x) || 000...
|| bits2octets(h1))

where '||' denotes concatenation. In other words, we compute
HMAC with key K, over the concatenation of the following, in
order: the current value of V, a sequence of eight bits of value
0, random data Z0 (of the same length as int2octets(x)), a
0, random data Zd (of the same length as int2octets(x)), a
sequence of zero bits 000..., the encoding of the (EC)DSA private
key x, a sequence of zero bits 000..., and the hashed message
(possibly truncated and extended as specified by the bits2octets
transform). The number of zeroes 000... is chosen so that the
length of (V || 0x00 || Z0 || 000...) and (int2octets(x) ||
length of (V || 0x00 || Zd || 000...) and (int2octets(x) ||
000...) are multiples of the block size of the hash function.
The HMAC result is the new value of K. Note that the private key
x is in the [1, q-1] range, hence a proper input for int2octets,
Expand All @@ -503,10 +503,10 @@ d. Set:
~~~~~~~~~~~~~~~~~~~~~~~
f. Set:

K = HMAC_K(V || 0x01 || Z1 || 000... || int2octets(x) ||
K = HMAC_K(V || 0x01 || Zf || 000... || int2octets(x) ||
000... || bits2octets(h1))

Note that the "internal octet" is 0x01 this time and that Z1 is
Note that the "internal octet" is 0x01 this time and that Zf is
newly generated random data, i.e., not reused from step (d).
~~~~~~~~~~~~~~~~~~~~~~~

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