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Deduplicate OCB encrypt / decrypt

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This commit is contained in:
Daniel Huigens 2018-04-24 13:22:53 +02:00
parent e8adeef278
commit bbf71d149b
2 changed files with 112 additions and 146 deletions
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256
src/crypto/ocb.js
View File

@ -66,30 +66,29 @@ const one = new Uint8Array([1]);
async function OCB(cipher, key) {
let maxNtz = 0;
let kv;
let encipher;
let decipher;
let mask;
constructKeyVariables(cipher, key);
function constructKeyVariables(cipher, key) {
const aes = new ciphers[cipher](key);
const encipher = aes.encrypt.bind(aes);
const decipher = aes.decrypt.bind(aes);
encipher = aes.encrypt.bind(aes);
decipher = aes.decrypt.bind(aes);
const mask_x = encipher(zeroBlock);
const mask_$ = util.double(mask_x);
const mask = [];
mask = [];
mask[0] = util.double(mask_$);
mask.x = mask_x;
mask.$ = mask_$;
kv = { encipher, decipher, mask };
}
function extendKeyVariables(text, adata) {
const { mask } = kv;
const newMaxNtz = util.nbits(Math.max(text.length, adata.length) >> 4) - 1;
const newMaxNtz = util.nbits(Math.max(text.length, adata.length) / blockLength | 0) - 1;
for (let i = maxNtz + 1; i <= newMaxNtz; i++) {
mask[i] = util.double(mask[i - 1]);
}
@ -102,19 +101,17 @@ async function OCB(cipher, key) {
return zeroBlock;
}
const { encipher, mask } = kv;
//
// Consider A as a sequence of 128-bit blocks
//
const m = adata.length >> 4;
const m = adata.length / blockLength | 0;
const offset = new Uint8Array(16);
const sum = new Uint8Array(16);
const offset = new Uint8Array(blockLength);
const sum = new Uint8Array(blockLength);
for (let i = 0; i < m; i++) {
xorMut(offset, mask[ntz(i + 1)]);
xorMut(sum, encipher(xor(offset, adata)));
adata = adata.subarray(16);
adata = adata.subarray(blockLength);
}
//
@ -123,7 +120,7 @@ async function OCB(cipher, key) {
if (adata.length) {
xorMut(offset, mask.x);
const cipherInput = new Uint8Array(16);
const cipherInput = new Uint8Array(blockLength);
cipherInput.set(adata, 0);
cipherInput[adata.length] = 0b10000000;
xorMut(cipherInput, offset);
@ -134,6 +131,92 @@ async function OCB(cipher, key) {
return sum;
}
/**
* Encrypt/decrypt data.
* @param {encipher|decipher} fn Encryption/decryption block cipher function
* @param {Uint8Array} text The cleartext or ciphertext (without tag) input
* @param {Uint8Array} nonce The nonce (15 bytes)
* @param {Uint8Array} adata Associated data to sign
* @returns {Promise<Uint8Array>} The ciphertext or plaintext output, with tag appended in both cases
*/
function crypt(fn, text, nonce, adata) {
//
// Consider P as a sequence of 128-bit blocks
//
const m = text.length / blockLength | 0;
//
// Key-dependent variables
//
extendKeyVariables(text, adata);
//
// Nonce-dependent and per-encryption variables
//
// Nonce = num2str(TAGLEN mod 128,7) || zeros(120-bitlen(N)) || 1 || N
// Note: We assume here that tagLength mod 16 == 0.
const paddedNonce = util.concatUint8Array([zeroBlock.subarray(0, ivLength - nonce.length), one, nonce]);
// bottom = str2num(Nonce[123..128])
const bottom = paddedNonce[blockLength - 1] & 0b111111;
// Ktop = ENCIPHER(K, Nonce[1..122] || zeros(6))
paddedNonce[blockLength - 1] &= 0b11000000;
const kTop = encipher(paddedNonce);
// Stretch = Ktop || (Ktop[1..64] xor Ktop[9..72])
const stretched = util.concatUint8Array([kTop, xor(kTop.subarray(0, 8), kTop.subarray(1, 9))]);
// Offset_0 = Stretch[1+bottom..128+bottom]
const offset = util.shiftRight(stretched.subarray(0 + (bottom >> 3), 17 + (bottom >> 3)), 8 - (bottom & 7)).subarray(1);
// Checksum_0 = zeros(128)
const checksum = new Uint8Array(blockLength);
const ct = new Uint8Array(text.length + tagLength);
//
// Process any whole blocks
//
let i;
let pos = 0;
for (i = 0; i < m; i++) {
// Offset_i = Offset_{i-1} xor L_{ntz(i)}
xorMut(offset, mask[ntz(i + 1)]);
// C_i = Offset_i xor ENCIPHER(K, P_i xor Offset_i)
// P_i = Offset_i xor DECIPHER(K, C_i xor Offset_i)
ct.set(xorMut(fn(xor(offset, text)), offset), pos);
// Checksum_i = Checksum_{i-1} xor P_i
xorMut(checksum, fn === encipher ? text : ct.subarray(pos));
text = text.subarray(blockLength);
pos += blockLength;
}
//
// Process any final partial block and compute raw tag
//
if (text.length) {
// Offset_* = Offset_m xor L_*
xorMut(offset, mask.x);
// Pad = ENCIPHER(K, Offset_*)
const padding = encipher(offset);
// C_* = P_* xor Pad[1..bitlen(P_*)]
ct.set(xor(text, padding), pos);
// Checksum_* = Checksum_m xor (P_* || 1 || new Uint8Array(127-bitlen(P_*)))
const xorInput = new Uint8Array(blockLength);
xorInput.set(fn === encipher ? text : ct.subarray(pos, -tagLength), 0);
xorInput[text.length] = 0b10000000;
xorMut(checksum, xorInput);
pos += text.length;
}
// Tag = ENCIPHER(K, Checksum_* xor Offset_* xor L_$) xor HASH(K,A)
const tag = xorMut(encipher(xorMut(xorMut(checksum, offset), mask.$)), hash(adata));
//
// Assemble ciphertext
//
// C = C_1 || C_2 || ... || C_m || C_* || Tag[1..TAGLEN]
ct.set(tag, pos);
return ct;
}
return {
/**
@ -144,145 +227,28 @@ async function OCB(cipher, key) {
* @returns {Promise<Uint8Array>} The ciphertext output
*/
encrypt: async function(plaintext, nonce, adata) {
//
// Consider P as a sequence of 128-bit blocks
//
const m = plaintext.length >> 4;
//
// Key-dependent variables
//
extendKeyVariables(plaintext, adata);
const { encipher, mask } = kv;
//
// Nonce-dependent and per-encryption variables
//
// We assume here that tagLength mod 16 == 0.
const paddedNonce = util.concatUint8Array([zeroBlock.subarray(0, 15 - nonce.length), one, nonce]);
const bottom = paddedNonce[15] & 0b111111;
paddedNonce[15] &= 0b11000000;
const kTop = encipher(paddedNonce);
const stretched = util.concatUint8Array([kTop, xor(kTop.subarray(0, 8), kTop.subarray(1, 9))]);
// Offset_0 = Stretch[1+bottom..128+bottom]
const offset = util.shiftRight(stretched.subarray(0 + (bottom >> 3), 17 + (bottom >> 3)), 8 - (bottom & 7)).subarray(1);
const checksum = new Uint8Array(16);
const ct = new Uint8Array(plaintext.length + tagLength);
//
// Process any whole blocks
//
let i;
let pos = 0;
for (i = 0; i < m; i++) {
xorMut(offset, mask[ntz(i + 1)]);
ct.set(xorMut(encipher(xor(offset, plaintext)), offset), pos);
xorMut(checksum, plaintext);
plaintext = plaintext.subarray(16);
pos += 16;
}
//
// Process any final partial block and compute raw tag
//
if (plaintext.length) {
xorMut(offset, mask.x);
const padding = encipher(offset);
ct.set(xor(plaintext, padding), pos);
// Checksum_* = Checksum_m xor (P_* || 1 || new Uint8Array(127-bitlen(P_*)))
const xorInput = new Uint8Array(16);
xorInput.set(plaintext, 0);
xorInput[plaintext.length] = 0b10000000;
xorMut(checksum, xorInput);
pos += plaintext.length;
}
const tag = xorMut(encipher(xorMut(xorMut(checksum, offset), mask.$)), hash(adata));
//
// Assemble ciphertext
//
ct.set(tag, pos);
return ct;
return crypt(encipher, plaintext, nonce, adata);
},
/**
* Decrypt ciphertext input.
* @param {Uint8Array} ciphertext The ciphertext input to be decrypted
* @param {Uint8Array} nonce The nonce (15 bytes)
* @param {Uint8Array} adata Associated data to verify
* @returns {Promise<Uint8Array>} The plaintext output
* @param {Uint8Array} ciphertext The ciphertext input to be decrypted
* @param {Uint8Array} nonce The nonce (15 bytes)
* @param {Uint8Array} adata Associated data to sign
* @returns {Promise<Uint8Array>} The ciphertext output
*/
decrypt: async function(ciphertext, nonce, adata) {
//
// Consider C as a sequence of 128-bit blocks
//
const ctTag = ciphertext.subarray(ciphertext.length - tagLength);
ciphertext = ciphertext.subarray(0, ciphertext.length - tagLength);
const m = ciphertext.length >> 4;
if (ciphertext.length < tagLength) throw new Error('Invalid OCB ciphertext');
//
// Key-dependent variables
//
extendKeyVariables(ciphertext, adata);
const { encipher, decipher, mask } = kv;
const tag = ciphertext.subarray(-tagLength);
ciphertext = ciphertext.subarray(0, -tagLength);
//
// Nonce-dependent and per-encryption variables
//
// We assume here that tagLength mod 16 == 0.
const paddedNonce = util.concatUint8Array([zeroBlock.subarray(0, 15 - nonce.length), one, nonce]);
const bottom = paddedNonce[15] & 0b111111;
paddedNonce[15] &= 0b11000000;
const kTop = encipher(paddedNonce);
const stretched = util.concatUint8Array([kTop, xor(kTop.subarray(0, 8), kTop.subarray(1, 9))]);
// Offset_0 = Stretch[1+bottom..128+bottom]
const offset = util.shiftRight(stretched.subarray(0 + (bottom >> 3), 17 + (bottom >> 3)), 8 - (bottom & 7)).subarray(1);
const checksum = new Uint8Array(16);
const pt = new Uint8Array(ciphertext.length);
//
// Process any whole blocks
//
let i;
let pos = 0;
for (i = 0; i < m; i++) {
xorMut(offset, mask[ntz(i + 1)]);
pt.set(xorMut(decipher(xor(offset, ciphertext)), offset), pos);
xorMut(checksum, pt.subarray(pos));
ciphertext = ciphertext.subarray(16);
pos += 16;
const crypted = crypt(decipher, ciphertext, nonce, adata);
// if (Tag[1..TAGLEN] == T)
if (util.equalsUint8Array(tag, crypted.subarray(-tagLength))) {
return crypted.subarray(0, -tagLength);
}
//
// Process any final partial block and compute raw tag
//
if (ciphertext.length) {
xorMut(offset, mask.x);
const padding = encipher(offset);
pt.set(xor(ciphertext, padding), pos);
// Checksum_* = Checksum_m xor (P_* || 1 || new Uint8Array(127-bitlen(P_*)))
const xorInput = new Uint8Array(16);
xorInput.set(pt.subarray(pos), 0);
xorInput[ciphertext.length] = 0b10000000;
xorMut(checksum, xorInput);
pos += ciphertext.length;
}
const tag = xorMut(encipher(xorMut(xorMut(checksum, offset), mask.$)), hash(adata));
//
// Check for validity and assemble plaintext
//
if (!util.equalsUint8Array(ctTag, tag)) {
throw new Error('Authentication tag mismatch in OCB ciphertext');
}
return pt;
throw new Error('Authentication tag mismatch in OCB ciphertext');
}
};
}

2
src/packet/sym_encrypted_aead_protected.js
View File

@ -165,4 +165,4 @@ SymEncryptedAEADProtected.prototype.crypt = async function (fn, key, data, final
} else {
return modeInstance[fn](data, this.iv);
}
}
};