57 lines
1.7 KiB
C++
57 lines
1.7 KiB
C++
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#include "stdafx.h"
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#include "secrets.h"
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//Derive a Short text Secret from a 256 bit random value and a sixty four bit integer
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using ristretto255::scalar, ristretto255::hash, ristretto255::hsh;
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std::array<char, 27> DeriveTextSecret(const scalar & blob, uint_fast64_t i){
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static constexpr std::array<uint8_t, crypto_pwhash_SALTBYTES> salt{0};
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std::array<char, 27> txt;
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unsigned int n{ 3 };
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unsigned int m{ 3 };
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hash rand(blob,i);
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uint8_t* p{ &rand.blob[0] };
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char* q = &txt[0];
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while (n || m) {
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if (*p++ < ((n * 0x100) / (n + m))) {
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n--;
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bits2base64(p, 0, 18, std::span(q, 4));
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q+=3;
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}
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else {
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m--;
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bits2base64(p, 0, 24, std::span(q, 5));
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q+=4;
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}
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*q++ = ' ';
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p += 3;
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}
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assert(q == sizeof(txt) + &txt[0]);
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assert(p == &rand.blob[24]);
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txt[sizeof(txt)-1]='\0';
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return txt;
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}
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//Derive a strong scalar secret from a string with password strengthening.
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//Net effect is convert one scalar into another by a process that is lengthy and costly.
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ristretto255::scalar DeriveStrongSecret(const char* const passwd){
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static std::array<uint8_t, crypto_pwhash_SALTBYTES> salt{ 0 };
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std::array<uint8_t, sizeof(ristretto255::hash<512>)>randb;
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int i{
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crypto_pwhash(
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&randb[0],
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sizeof(randb),
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passwd,
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strlen(passwd)+1,
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&salt[0],
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2, 0x10000000,
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crypto_pwhash_ALG_ARGON2ID13
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)
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};
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static_assert(crypto_pwhash_OPSLIMIT_MODERATE == 0x00000003 && crypto_pwhash_MEMLIMIT_MODERATE == 0x10000000, "Argon changed, likely breaking all passphrases");
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assert(i == 0);
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return scalar(hash<512>(randb));
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}
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//Derive scalar secret from another quickly.
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ristretto255::scalar DeriveSecret(const scalar &sc, uint_fast64_t i) {
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return ristretto255::scalar(ristretto255::hash<512>(sc, i));
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}
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