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import fe1 from 'node-fe1-fpe' | |
export interface IFPESetting { | |
min: number | |
max: number | |
privateKey: string | |
publicKey: string | |
} | |
export const encrypt = ({ | |
index, | |
min, | |
max, | |
privateKey, | |
publicKey, | |
}: IFPESetting & { | |
index: number | |
}): number => { | |
// Algorithm can be applied only when the difference | |
// between the min and max values is at least 4. | |
if (max - min < 3) return index | |
// Algorithms can only be applied when the | |
// range difference between min and max is prime number. | |
// Therefore, when the range difference is not prime number, | |
// the algorithm is applied while leaving the last index intact. | |
// if ((max - min) % 2 === 0) { | |
// if (index === max) return index | |
// --max | |
// } | |
if ((max - min) % 2 === 0) { | |
// console.log('enc yes') | |
const middle = Math.ceil(min + (max - min) / 2) | |
// console.log('encrypted middle', middle) | |
if (index === middle) return max | |
if (index === max) index = middle | |
--max | |
} | |
// Algorithm does not apply to index | |
// values that are not in the range. | |
if (index < min || index > max) return index | |
return fe1.encrypt(max - min + 1, index - min, privateKey, publicKey) + min | |
} | |
export const decrypt = ({ | |
index, | |
min, | |
max, | |
privateKey, | |
publicKey, | |
}: IFPESetting & { | |
index: number | |
}): number => { | |
// Algorithm can be applied only when the difference | |
// between the min and max values is at least 4. | |
if (max - min < 3) return index | |
// Algorithms can only be applied when the | |
// range difference between min and max is prime number. | |
// Therefore, when the range difference is not prime number, | |
// the algorithm is applied while leaving the last index intact. | |
const isNonPrime = (max - min) % 2 === 0 | |
if (isNonPrime) { | |
if (index > max - 1) { | |
return Math.ceil(min + (max - min) / 2) | |
} | |
--max | |
} | |
// Algorithm does not apply to index | |
// values that are not in the range. | |
if (index < min || index > max) return index | |
if (isNonPrime) { | |
if ( | |
index === | |
encrypt({ | |
index: Math.ceil(min + (max - min) / 2), | |
max, | |
min, | |
privateKey, | |
publicKey, | |
}) | |
) | |
return max + 1 | |
} | |
return fe1.decrypt(max - min + 1, index - min, privateKey, publicKey) + min | |
} | |
const settings: IFPESetting = { | |
min: -5, | |
max: 100, | |
privateKey: 'some private string', | |
publicKey: 'some public string', | |
} | |
for (let i = -8; i <= 102; i++) { | |
const encrypted = encrypt({ | |
index: i, | |
...settings, | |
}) | |
const decrypted = decrypt({ | |
index: encrypted, | |
...settings, | |
}) | |
console.log(i, encrypted, decrypted) | |
} |
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