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ChaCha20 Explicitly Set Counter #1010

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ChaCha20 Explicitly Set Counter #1010

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a2c4131
Added counter param to ChaCha20 initializer, defaulting to original v…
btoms20 Apr 10, 2023
3034000
Added explicitly set counter tests.
btoms20 Apr 10, 2023
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10 changes: 6 additions & 4 deletions Sources/CryptoSwift/ChaCha20.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -28,8 +28,8 @@ public final class ChaCha20: BlockCipher {
fileprivate let key: Key
fileprivate var counter: Array<UInt8>

public init(key: Array<UInt8>, iv nonce: Array<UInt8>) throws {
precondition(nonce.count == 12 || nonce.count == 8)
public init(key: Array<UInt8>, counter: Array<UInt8> = [0, 0, 0, 0], iv nonce: Array<UInt8>) throws {
precondition(counter.count == 4 && (nonce.count == 12 || nonce.count == 8))

if key.count != 32 {
throw Error.invalidKeyOrInitializationVector
Expand All @@ -39,9 +39,11 @@ public final class ChaCha20: BlockCipher {
self.keySize = self.key.count

if nonce.count == 8 {
self.counter = [0, 0, 0, 0, 0, 0, 0, 0] + nonce
self.counter = counter + [0, 0, 0, 0] + nonce
} else if nonce.count == 12 {
self.counter = counter + nonce
} else {
self.counter = [0, 0, 0, 0] + nonce
throw Error.invalidKeyOrInitializationVector
}

assert(self.counter.count == 16)
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34 changes: 33 additions & 1 deletion Tests/CryptoSwiftTests/ChaCha20Tests.swift
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Expand Up @@ -106,6 +106,36 @@ final class ChaCha20Tests: XCTestCase {
XCTFail()
}
}

/// Test Vector - https://datatracker.ietf.org/doc/html/rfc9001#name-chacha20-poly1305-short-hea
func testChaCha20ExplicitCounterV1() {
let hpKey = Array(hex: "0x25a282b9e82f06f21f488917a4fc8f1b73573685608597d0efcb076b0ab7a7a4")
/// Sample = 0x5e5cd55c41f69080575d7999c25a5bfb
let counter = Array(hex: "0x5e5cd55c")
let iv = Array(hex: "0x41f69080575d7999c25a5bfb")

do {
let mask = try CryptoSwift.ChaCha20(key: hpKey, counter: counter, iv: iv).encrypt(Array<UInt8>(repeating: 0, count: 5))
XCTAssertEqual(mask, Array(hex: "0xaefefe7d03"))
} catch {
XCTFail("\(error)")
}
}

/// Test Vector - https://www.ietf.org/archive/id/draft-ietf-quic-v2-10.html#name-chacha20-poly1305-short-head
func testChaCha20ExplicitCounterV2() {
let hpKey = Array(hex: "0xd659760d2ba434a226fd37b35c69e2da8211d10c4f12538787d65645d5d1b8e2")
/// Sample = 0xe7b6b932bc27d786f4bc2bb20f2162ba
let counter = Array(hex: "0xe7b6b932")
let iv = Array(hex: "0xbc27d786f4bc2bb20f2162ba")

do {
let mask = try CryptoSwift.ChaCha20(key: hpKey, counter: counter, iv: iv).encrypt(Array<UInt8>(repeating: 0, count: 5))
XCTAssertEqual(mask, Array(hex: "0x97580e32bf"))
} catch {
XCTFail("\(error)")
}
}
}

extension ChaCha20Tests {
Expand All @@ -114,7 +144,9 @@ extension ChaCha20Tests {
("testChaCha20", testChaCha20),
("testCore", testCore),
("testVector1Py", testVector1Py),
("testChaCha20EncryptPartial", testChaCha20EncryptPartial)
("testChaCha20EncryptPartial", testChaCha20EncryptPartial),
("testChaCha20ExplicitCounterV1", testChaCha20ExplicitCounterV1),
("testChaCha20ExplicitCounterV2", testChaCha20ExplicitCounterV2)
]

return tests
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