class Lightning::Onion::ChaCha20::Pure
Public Class Methods
chacha20_encrypt(key, counter, nonce, plaintext)
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# File lib/lightning/onion/chacha20/pure.rb, line 8 def self.chacha20_encrypt(key, counter, nonce, plaintext) encrypted_message = +'' (plaintext.length / 64).times do |i| key_stream = chacha20_block(key, counter + i, nonce) block = plaintext[(i * 64)...(i + 1) * 64] encrypted_message += xor(block, key_stream) end if plaintext.length % 64 != 0 i = plaintext.length / 64 key_stream = chacha20_block(key, counter + i, nonce) block = plaintext[(i * 64)...plaintext.length] block = block.ljust(64, "\x00") encrypted_message += xor(block, key_stream)[0...(plaintext.length % 64)] end encrypted_message end
Private Class Methods
chacha20_block(key, counter, nonce)
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key: 32 bytes counter: integer (4 bytes) nonce: 12 bytes
# File lib/lightning/onion/chacha20/pure.rb, line 40 def self.chacha20_block(key, counter, nonce) # reverse order key = key.unpack('V*').pack('N*') counter = [counter].pack('N*') nonce = nonce.unpack('V*').pack('N*') state = constants + key + counter + nonce working_state = state.unpack('N*') 10.times do inner_block(working_state) end plus_for_string(state, working_state) end
constants()
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# File lib/lightning/onion/chacha20/pure.rb, line 27 def self.constants [0x61707865, 0x3320646e, 0x79622d32, 0x6b206574].pack('N*') end
inner_block(x)
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# File lib/lightning/onion/chacha20/pure.rb, line 53 def self.inner_block(x) # column rounds x[0], x[4], x[8], x[12] = quater_round(x[0], x[4], x[8], x[12]) x[1], x[5], x[9], x[13] = quater_round(x[1], x[5], x[9], x[13]) x[2], x[6], x[10], x[14] = quater_round(x[2], x[6], x[10], x[14]) x[3], x[7], x[11], x[15] = quater_round(x[3], x[7], x[11], x[15]) # diagonal rounds x[0], x[5], x[10], x[15] = quater_round(x[0], x[5], x[10], x[15]) x[1], x[6], x[11], x[12] = quater_round(x[1], x[6], x[11], x[12]) x[2], x[7], x[8], x[13] = quater_round(x[2], x[7], x[8], x[13]) x[3], x[4], x[9], x[14] = quater_round(x[3], x[4], x[9], x[14]) end
plus(x, y)
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# File lib/lightning/onion/chacha20/pure.rb, line 72 def self.plus(x, y) (x + y) & 0xffffffff end
plus_for_string(a, b)
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# File lib/lightning/onion/chacha20/pure.rb, line 66 def self.plus_for_string(a, b) a.unpack('N*').map.with_index do |x, i| plus(x, b[i]) end.pack('V*') end
quater_round(a, b, c, d)
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# File lib/lightning/onion/chacha20/pure.rb, line 82 def self.quater_round(a, b, c, d) a = plus(a, b) d ^= a d = rotate(d, 16) c = plus(c, d) b ^= c b = rotate(b, 12) a = plus(a, b) d ^= a d = rotate(d, 8) c = plus(c, d) b ^= c b = rotate(b, 7) [a, b, c, d] end
rotate(x, n)
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# File lib/lightning/onion/chacha20/pure.rb, line 76 def self.rotate(x, n) y = x << n z = x >> (32 - n) (y | z) & 0xffffffff end
xor(a, b)
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# File lib/lightning/onion/chacha20/pure.rb, line 31 def self.xor(a, b) a = a.unpack('N*') b = b.unpack('N*') a.zip(b).map { |x, y| (x ^ y) & 0xffffffff }.pack('N*') end