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| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 | 41x 23x 23x 41x 20x 20x 41x 4x 4x 1x 4x 4x 4x 4x 41x 1x 1x 1x 1x 41x 4x 4x 4x 3x 1x 1x 4x 3x 1x 1x | import { CipherObject, CipherTextEncoding, SignedCipherObject } from './types';
/**
* Calculate the AES-CBC ciphertext output byte length a given input length.
* AES has a fixed block size of 16-bytes regardless key size.
* @ignore
*/
export function getAesCbcOutputLength(inputByteLength: number) {
// AES-CBC block mode rounds up to the next block size.
const cipherTextLength = (Math.floor(inputByteLength / 16) + 1) * 16;
return cipherTextLength;
}
/**
* Calculate the base64 encoded string length for a given input length.
* This is equivalent to the byte length when the string is ASCII or UTF8-8
* encoded.
* @param inputByteLength
*/
export function getBase64OutputLength(inputByteLength: number) {
const encodedLength = Math.ceil(inputByteLength / 3) * 4;
return encodedLength;
}
/**
* Fast function that determines the final ASCII string byte length of the
* JSON stringified ECIES encrypted payload.
* @ignore
*/
/**
* Get details about the JSON envelope size overhead for ciphertext payloads.
* @ignore
*/
export function getCipherObjectWrapper(opts: {
wasString: boolean;
cipherTextEncoding: CipherTextEncoding;
}): {
/** The stringified JSON string of an empty `CipherObject`. */
payloadShell: string;
/** Total string length of all the `CipherObject` values that always have constant lengths. */
payloadValuesLength: number;
} {
// Placeholder structure of the ciphertext payload, used to determine the
// stringified JSON overhead length.
const shell: CipherObject = {
iv: '',
ephemeralPK: '',
mac: '',
cipherText: '',
wasString: !!opts.wasString,
};
if (opts.cipherTextEncoding === 'base64') {
shell.cipherTextEncoding = 'base64';
}
// Hex encoded 16 byte buffer.
const ivLength = 32;
// Hex encoded, compressed EC pubkey of 33 bytes.
const ephemeralPKLength = 66;
// Hex encoded 32 byte hmac-sha256.
const macLength = 64;
return {
payloadValuesLength: ivLength + ephemeralPKLength + macLength,
payloadShell: JSON.stringify(shell),
};
}
/**
* Get details about the JSON envelope size overhead for signed ciphertext payloads.
* @param payloadShell - The JSON stringified empty `CipherObject`
* @ignore
*/
export function getSignedCipherObjectWrapper(payloadShell: string): {
/** The stringified JSON string of an empty `SignedCipherObject`. */
signedPayloadValuesLength: number;
/** Total string length of all the `SignedCipherObject` values
* that always have constant lengths */
signedPayloadShell: string;
} {
// Placeholder structure of the signed ciphertext payload, used to determine the
// stringified JSON overhead length.
const shell: SignedCipherObject = {
signature: '',
publicKey: '',
cipherText: payloadShell,
};
// Hex encoded DER signature, up to 72 byte length.
const signatureLength = 144;
// Hex encoded 33 byte public key.
const publicKeyLength = 66;
return {
signedPayloadValuesLength: signatureLength + publicKeyLength,
signedPayloadShell: JSON.stringify(shell),
};
}
export function eciesGetJsonStringLength(opts: {
contentLength: number;
wasString: boolean;
sign: boolean;
cipherTextEncoding: CipherTextEncoding;
}): number {
const { payloadShell, payloadValuesLength } = getCipherObjectWrapper(opts);
// Calculate the AES output length given the input length.
const cipherTextLength = getAesCbcOutputLength(opts.contentLength);
// Get the encoded string length of the cipherText.
let encodedCipherTextLength: number;
if (!opts.cipherTextEncoding || opts.cipherTextEncoding === 'hex') {
encodedCipherTextLength = cipherTextLength * 2;
} else if (opts.cipherTextEncoding === 'base64') {
encodedCipherTextLength = getBase64OutputLength(cipherTextLength);
} else E{
throw new Error(`Unexpected cipherTextEncoding "${opts.cipherTextEncoding}"`);
}
if (!opts.sign) {
// Add the length of the JSON envelope, ciphertext length, and length of const values.
return payloadShell.length + payloadValuesLength + encodedCipherTextLength;
} else {
// Get the signed version of the JSON envelope
const { signedPayloadShell, signedPayloadValuesLength } =
getSignedCipherObjectWrapper(payloadShell);
// Add length of the JSON envelope, ciphertext length, and length of the const values.
return (
signedPayloadShell.length +
signedPayloadValuesLength +
payloadValuesLength +
encodedCipherTextLength
);
}
}
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