var parseKeys = require('parse-asn1')
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var randomBytes = require('randombytes')
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var createHash = require('create-hash')
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var mgf = require('./mgf')
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var xor = require('./xor')
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var BN = require('bn.js')
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var withPublic = require('./withPublic')
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var crt = require('browserify-rsa')
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var Buffer = require('safe-buffer').Buffer
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module.exports = function publicEncrypt (publicKey, msg, reverse) {
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var padding
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if (publicKey.padding) {
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padding = publicKey.padding
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} else if (reverse) {
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padding = 1
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} else {
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padding = 4
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}
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var key = parseKeys(publicKey)
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var paddedMsg
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if (padding === 4) {
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paddedMsg = oaep(key, msg)
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} else if (padding === 1) {
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paddedMsg = pkcs1(key, msg, reverse)
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} else if (padding === 3) {
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paddedMsg = new BN(msg)
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if (paddedMsg.cmp(key.modulus) >= 0) {
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throw new Error('data too long for modulus')
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}
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} else {
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throw new Error('unknown padding')
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}
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if (reverse) {
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return crt(paddedMsg, key)
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} else {
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return withPublic(paddedMsg, key)
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}
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}
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function oaep (key, msg) {
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var k = key.modulus.byteLength()
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var mLen = msg.length
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var iHash = createHash('sha1').update(Buffer.alloc(0)).digest()
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var hLen = iHash.length
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var hLen2 = 2 * hLen
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if (mLen > k - hLen2 - 2) {
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throw new Error('message too long')
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}
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var ps = Buffer.alloc(k - mLen - hLen2 - 2)
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var dblen = k - hLen - 1
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var seed = randomBytes(hLen)
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var maskedDb = xor(Buffer.concat([iHash, ps, Buffer.alloc(1, 1), msg], dblen), mgf(seed, dblen))
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var maskedSeed = xor(seed, mgf(maskedDb, hLen))
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return new BN(Buffer.concat([Buffer.alloc(1), maskedSeed, maskedDb], k))
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}
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function pkcs1 (key, msg, reverse) {
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var mLen = msg.length
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var k = key.modulus.byteLength()
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if (mLen > k - 11) {
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throw new Error('message too long')
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}
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var ps
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if (reverse) {
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ps = Buffer.alloc(k - mLen - 3, 0xff)
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} else {
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ps = nonZero(k - mLen - 3)
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}
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return new BN(Buffer.concat([Buffer.from([0, reverse ? 1 : 2]), ps, Buffer.alloc(1), msg], k))
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}
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function nonZero (len) {
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var out = Buffer.allocUnsafe(len)
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var i = 0
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var cache = randomBytes(len * 2)
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var cur = 0
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var num
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while (i < len) {
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if (cur === cache.length) {
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cache = randomBytes(len * 2)
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cur = 0
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}
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num = cache[cur++]
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if (num) {
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out[i++] = num
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}
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}
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return out
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}
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