35 lines
973 B
OCaml
35 lines
973 B
OCaml
module Kdf = struct
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module XTR = Hkdf.Make (Digestif.SHA512)
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module PRF = Hkdf.Make (Digestif.SHA256)
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let kdf ~xts ~ikm ~ctx ~len =
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let prk = XTR.extract ~salt:xts ikm in
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let okm = PRF.expand ~prk ~info:ctx len in
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okm
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end
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let kdf_mod_n ~n ~xts ~ikm ~ctx =
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let nbits = Z.numbits n in
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let len = ((nbits - 1) / 8) + 1 in
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assert (8 * len = nbits);
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let rec go ctr =
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let ctr_be =
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let b = Bytes.create 2 in
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Bytes.set_uint16_be b 0 ctr;
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Bytes.unsafe_to_string b
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in
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let ctx = String.cat ctx ctr_be in
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let okm = Kdf.kdf ~xts ~ikm ~ctx ~len in
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assert (String.length okm = len);
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let r = Mirage_crypto_pk.Z_extra.of_octets_be okm in
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if Z.gt r n then go (succ ctr) else r
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in
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go 0
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(*
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let rsa_sign_fdh priv msg =
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let pub = Mirage_crypto_pk.Rsa.pub_of_priv priv in
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let v = rsa_full_domain_hash pub msg in
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let v = Z.to_bits v in
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Mirage_crypto_pk.Rsa.PKCS1.sig_encode ~crt_hardening:true ~key:priv v
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*)
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