x.crypto.ascon: improve the core of Ascon permutation routine (#25278)

blackshirt · web-flow · commit f16452d3a65f · 2025-09-11T05:56:17.000+03:00
diff --git a/vlib/x/crypto/ascon/README.md b/vlib/x/crypto/ascon/README.md
@@ -1,15 +1,17 @@
 # ascon
 
-`ascon` is a implementation of Ascon-Based Cryptography module implemented in pure V language.
+`ascon` is an implementation of Ascon-Based Cryptography module implemented in pure V language.
 This module was mostly based on NIST Special Publication of 800 NIST SP 800-232 document.
 Its describes an Ascon-Based Lightweight Cryptography Standards for Constrained Devices 
 thats provides Authenticated Encryption, Hash, and Extendable Output Functions.
 See the [NIST.SP.800-232 Standard](https://doi.org/10.6028/NIST.SP.800-232) for more detail.
 
-This module does not fully implements all the features availables on the document.
+This module mostly implements all the features availables on the document.
 Its currently implements:
 - `Ascon-Hash256`, Ascon-based hashing implementation that produces 256-bits output.
-- `Ascon-XOF128`, Ascon-based eXtendible Output Function (XOF) where the output size of 
+- `Ascon-XOF128`, Ascon-based eXtendable Output Function (XOF) where the output size of 
 the hash of the message can be selected by the user.
 - `Ascon-CXOF128`, a customized XOF that allows users to specify a customization
 string and choose the output size of the message hash.
+- `Ascon-AEAD128`, an Authenticated Encryption with Additional Data (AEAD) Scheme based
+on Ascon-family crypto.
diff --git a/vlib/x/crypto/ascon/aead128.v b/vlib/x/crypto/ascon/aead128.v
@@ -181,7 +181,7 @@ pub fn (mut c Aead128) encrypt(msg []u8, nonce []u8, ad []u8) ![]u8 {
 	c.State.e4 = n1
 
 	// Update state by permutation
-	ascon_pnr(mut c.State, 12)
+	ascon_pnr(mut c.State, ascon_prnd_12)
 	// XOR-ing with the cipher's key
 	c.State.e3 ^= c.key[0]
 	c.State.e4 ^= c.key[1]
@@ -229,7 +229,7 @@ pub fn (mut c Aead128) decrypt(ciphertext []u8, nonce []u8, ad []u8) ![]u8 {
 	c.State.e4 = n1
 
 	// scrambled with permutation routine
-	ascon_pnr(mut c.State, 12)
+	ascon_pnr(mut c.State, ascon_prnd_12)
 	// xor-ing with the cipher's key
 	c.State.e3 ^= c.key[0]
 	c.State.e4 ^= c.key[1]
@@ -288,7 +288,7 @@ fn aead128_init(mut s State, key []u8, nonce []u8) (u64, u64) {
 	s.e4 = n1
 
 	// updates State using the permutation 𝐴𝑠𝑐𝑜𝑛-𝑝[12], S ← 𝐴𝑠𝑐𝑜𝑛-𝑝[12](S)
-	ascon_pnr(mut s, 12)
+	ascon_pnr(mut s, ascon_prnd_12)
 
 	// Then XORing the secret key 𝐾 into the last 128 bits of internal state:
 	// S ← S ⊕ (0¹⁹² ∥ 𝐾).
@@ -312,7 +312,7 @@ fn aead128_process_ad(mut s State, ad []u8) {
 			s.e1 ^= binary.little_endian_u64(block[8..16])
 
 			// Apply permutation 𝐴𝑠𝑐𝑜𝑛-𝑝[8] to the state
-			ascon_pnr(mut s, 8)
+			ascon_pnr(mut s, ascon_prnd_8)
 			// Updates index
 			ad_length -= aead128_block_size
 			ad_idx += aead128_block_size
@@ -339,7 +339,7 @@ fn aead128_process_ad(mut s State, ad []u8) {
 			}
 		}
 		// Apply permutation 𝐴𝑠𝑐𝑜𝑛-𝑝[8] to the state
-		ascon_pnr(mut s, 8)
+		ascon_pnr(mut s, ascon_prnd_8)
 	}
 	// The final step of processing associated data is to update the state
 	// with a constant that provides domain separation.
@@ -361,7 +361,7 @@ fn aead128_process_msg(mut out []u8, mut s State, msg []u8) int {
 		binary.little_endian_put_u64(mut out[pos..pos + 8], s.e0)
 		binary.little_endian_put_u64(mut out[pos + 8..], s.e1)
 		// apply permutation
-		ascon_pnr(mut s, 8)
+		ascon_pnr(mut s, ascon_prnd_8)
 
 		// updates index
 		mlen -= aead128_block_size
@@ -413,7 +413,7 @@ fn aead128_partial_dec(mut out []u8, mut s State, cmsg []u8) {
 		s.e0 = c0
 		s.e1 = c1
 
-		ascon_pnr(mut s, 8)
+		ascon_pnr(mut s, ascon_prnd_8)
 		// updates index
 		pos += aead128_block_size
 		cmsg_len -= aead128_block_size
@@ -448,7 +448,7 @@ fn aead128_finalize(mut s State, k0 u64, k1 u64) {
 	s.e2 ^= k0
 	s.e3 ^= k1
 	// then updated using the permutation 𝐴𝑠𝑐𝑜𝑛-𝑝[12]
-	ascon_pnr(mut s, 12)
+	ascon_pnr(mut s, ascon_prnd_12)
 
 	// Finally, the tag 𝑇 is generated by XORing the key with the last 128 bits of the state:
 	// 𝑇 ← 𝑆[192∶319] ⊕ 𝐾.
diff --git a/vlib/x/crypto/ascon/ascon.v b/vlib/x/crypto/ascon/ascon.v
@@ -10,6 +10,10 @@ module ascon
 // constants for up to 16 rounds to accommodate potential functionality extensions in the future.
 const max_nr_perm = 16
 
+// The number how many round(s) for the Ascon permutation routine called.
+const ascon_prnd_8 = 8
+const ascon_prnd_12 = 12
+
 // The constants to derive round constants of the Ascon permutations
 // See Table 5. of NIST SP 800-232 docs
 //
@@ -26,70 +30,72 @@ const max_nr_perm = 16
 const rnc = [u8(0x3c), 0x2d, 0x1e, 0x0f, 0xf0, 0xe1, 0xd2, 0xc3, 0xb4, 0xa5, 0x96, 0x87, 0x78,
 	0x69, 0x5a, 0x4b]
 
-// ascon_pnr is ascon permutation routine with specified numbers of round nr, where 1 ≤ nr ≤ 16
+// ascon_pnr is the core of Ascon family permutation routine with specified numbers of round nr, where 1 ≤ nr ≤ 16
+// Its consist of iterations of the round function that is defined as the composition of three steps, ie:
+// 1. the constant-addition layer (see Sec. 3.2),
+// 2. the substitution layer (see Sec.3.3), and,
+// 3. the linear diffusion layer (Sec 3.4)
 @[direct_array_access]
 fn ascon_pnr(mut s State, nr int) {
 	// We dont allow nr == 0
 	if nr < 1 || nr > 16 {
 		panic('Invalid round number')
 	}
+	// Ascon permutation routine
 	for i := max_nr_perm - nr; i < max_nr_perm; i++ {
-		ascon_perm(mut s, rnc[i])
-	}
-}
+		// 3.2 Constant-Addition Layer step
+		//
+		// The constant-addition layer adds a 64-bit round constant 𝑐𝑖
+		// to 𝑆₂ in round 𝑖, for 𝑖 ≥ 0, ie, this is equivalent to applying
+		// the constant to only the least significant eight bits of 𝑆₂
+		s.e2 ^= rnc[i]
 
-// ascon_perm was the main permutations routine in Ascon-family crypto. Its consist of
-// iterations of the round function that is defined as the composition of three steps, ie:
-// 1. the constant-addition layer (see Sec. 3.2),
-// 2. the substitution layer (see Sec.3.3), and,
-// 3. the linear diffusion layer
-fn ascon_perm(mut s State, c u8) {
-	// 3.2 Constant-Addition Layer step
-	//
-	// The constant-addition layer adds a 64-bit round constant 𝑐𝑖
-	// to 𝑆₂ in round 𝑖, for 𝑖 ≥ 0, ie, this is equivalent to applying
-	// the constant to only the least significant eight bits of 𝑆₂
-	s.e2 ^= c
-
-	// 3.3. Substitution Layer
-	// The substitution layer updates the state S with 64 parallel applications of the 5-bit
-	// substitution box SBOX
-	s.e0 ^= s.e4
-	s.e4 ^= s.e3
-	s.e2 ^= s.e1
+		// 3.3. Substitution Layer
+		// The substitution layer updates the state S with 64 parallel applications of the 5-bit
+		// substitution box SBOX
+		s.e0 ^= s.e4
+		s.e4 ^= s.e3
+		s.e2 ^= s.e1
 
-	t0 := s.e4 ^ (~s.e0 & s.e1)
-	t1 := s.e0 ^ (~s.e1 & s.e2)
-	t2 := s.e1 ^ (~s.e2 & s.e3)
-	t3 := s.e2 ^ (~s.e3 & s.e4)
-	t4 := s.e3 ^ (~s.e4 & s.e0)
+		t0 := s.e4 ^ (~s.e0 & s.e1)
+		t1 := s.e0 ^ (~s.e1 & s.e2)
+		t2 := s.e1 ^ (~s.e2 & s.e3)
+		t3 := s.e2 ^ (~s.e3 & s.e4)
+		t4 := s.e3 ^ (~s.e4 & s.e0)
 
-	s.e0 = t1
-	s.e1 = t2
-	s.e2 = t3
-	s.e3 = t4
-	s.e4 = t0
+		s.e0 = t1
+		s.e1 = t2
+		s.e2 = t3
+		s.e3 = t4
+		s.e4 = t0
 
-	s.e1 ^= s.e0
-	s.e0 ^= s.e4
-	s.e3 ^= s.e2
-	s.e2 = ~(s.e2)
+		s.e1 ^= s.e0
+		s.e0 ^= s.e4
+		s.e3 ^= s.e2
+		s.e2 = ~(s.e2)
 
-	// 3.4. Linear Diffusion Layer
-	//
-	// The linear diffusion layer provides diffusion within each 64-bit word S,
-	// defined as :
-	// 		Σ0(𝑆0) = 𝑆0 ⊕ (𝑆0 ⋙ 19) ⊕ (𝑆0 ⋙ 28)
-	// 		Σ1(𝑆1) = 𝑆1 ⊕ (𝑆1 ⋙ 61) ⊕ (𝑆1 ⋙ 39)
-	// 		Σ2(𝑆2) = 𝑆2 ⊕ (𝑆2 ⋙ 1) ⊕ (𝑆2 ⋙ 6)
-	// 		Σ3(𝑆3) = 𝑆3 ⊕ (𝑆3 ⋙ 10) ⊕ (𝑆3 ⋙ 17)
-	// 		Σ4(𝑆4) = 𝑆4 ⊕ (𝑆4 ⋙ 7) ⊕ (𝑆4 ⋙ 41)
-
-	s.e0 ^= ascon_rotate_right(s.e0, 19) ^ ascon_rotate_right(s.e0, 28)
-	s.e1 ^= ascon_rotate_right(s.e1, 61) ^ ascon_rotate_right(s.e1, 39)
-	s.e2 ^= ascon_rotate_right(s.e2, 1) ^ ascon_rotate_right(s.e2, 6)
-	s.e3 ^= ascon_rotate_right(s.e3, 10) ^ ascon_rotate_right(s.e3, 17)
-	s.e4 ^= ascon_rotate_right(s.e4, 7) ^ ascon_rotate_right(s.e4, 41)
+		// 3.4. Linear Diffusion Layer
+		//
+		// The linear diffusion layer provides diffusion within each 64-bit word S,
+		// defined as :
+		// 		Σ0(𝑆0) = 𝑆0 ⊕ (𝑆0 ⋙ 19) ⊕ (𝑆0 ⋙ 28)
+		// 		Σ1(𝑆1) = 𝑆1 ⊕ (𝑆1 ⋙ 61) ⊕ (𝑆1 ⋙ 39)
+		// 		Σ2(𝑆2) = 𝑆2 ⊕ (𝑆2 ⋙ 1) ⊕ (𝑆2 ⋙ 6)
+		// 		Σ3(𝑆3) = 𝑆3 ⊕ (𝑆3 ⋙ 10) ⊕ (𝑆3 ⋙ 17)
+		// 		Σ4(𝑆4) = 𝑆4 ⊕ (𝑆4 ⋙ 7) ⊕ (𝑆4 ⋙ 41)
+		//
+		// This diffusion layer, especially on the bits right rotation part is a most widely called
+		// for Ascon permutation routine. So, even bits rotation almost efficient on most platform,
+		// to reduce overhead on function call, we work on the raw bits right rotation here.
+		// Bits right rotation, basically can be defined as:
+		// 		ror = (x >> n) | x << (64 - n) for some u64 x
+		//
+		s.e0 ^= (s.e0 >> 19 | (s.e0 << (64 - 19))) ^ (s.e0 >> 28 | (s.e0 << (64 - 28)))
+		s.e1 ^= (s.e1 >> 61 | (s.e1 << (64 - 61))) ^ (s.e1 >> 39 | (s.e1 << (64 - 39)))
+		s.e2 ^= (s.e2 >> 1 | (s.e2 << (64 - 1))) ^ (s.e2 >> 6 | (s.e2 << (64 - 6))) // 	
+		s.e3 ^= (s.e3 >> 10 | (s.e3 << (64 - 10))) ^ (s.e3 >> 17 | (s.e3 << (64 - 17)))
+		s.e4 ^= (s.e4 >> 7 | (s.e4 << (64 - 7))) ^ (s.e4 >> 41 | (s.e4 << (64 - 41)))
+	}
 }
 
 // State is structure represents Ascon state. Its operates on the 320-bit opaque,
diff --git a/vlib/x/crypto/ascon/ascon_test.v b/vlib/x/crypto/ascon/ascon_test.v
@@ -5,23 +5,6 @@
 module ascon
 
 // This test mostly taken from https://docs.rs/ascon/latest/src/ascon/lib.rs.html
-fn test_ascon_round_one() {
-	mut s := State{
-		e0: u64(0x0123456789abcdef)
-		e1: 0x23456789abcdef01
-		e2: 0x456789abcdef0123
-		e3: 0x6789abcdef012345
-		e4: 0x89abcde01234567f
-	}
-	ascon_perm(mut s, 0x1f)
-
-	assert s.e0 == u64(0x3c1748c9be2892ce)
-	assert s.e1 == u64(0x5eafb305cd26164f)
-	assert s.e2 == u64(0xf9470254bb3a4213)
-	assert s.e3 == u64(0xf0428daf0c5d3948)
-	assert s.e4 == u64(0x281375af0b294899)
-}
-
 fn test_ascon_round_p6() {
 	mut s := State{
 		e0: u64(0x0123456789abcdef)
diff --git a/vlib/x/crypto/ascon/digest.v b/vlib/x/crypto/ascon/digest.v
@@ -33,7 +33,7 @@ fn (mut d Digest) finish() {
 	d.State.e0 ^= load_bytes(d.buf[..d.length], d.length)
 
 	// Permutation step was done in squeezing-phase
-	// ascon_pnr(mut d.State, 12)
+	// ascon_pnr(mut d.State, ascon_prnd_12)
 
 	// zeroing Digest buffer
 	d.length = 0
@@ -70,7 +70,7 @@ fn (mut d Digest) absorb(msg_ []u8) int {
 				// If this d.buf length has reached block_size bytes, absorb it.
 				if d.length == block_size {
 					d.State.e0 ^= binary.little_endian_u64(d.buf)
-					ascon_pnr(mut d.State, 12)
+					ascon_pnr(mut d.State, ascon_prnd_12)
 					// reset the internal buffer
 					d.length = 0
 					d.buf.reset()
@@ -87,7 +87,7 @@ fn (mut d Digest) absorb(msg_ []u8) int {
 		for msg.len >= block_size {
 			d.State.e0 ^= binary.little_endian_u64(msg[0..block_size])
 			msg = msg[block_size..]
-			ascon_pnr(mut d.State, 12)
+			ascon_pnr(mut d.State, ascon_prnd_12)
 		}
 		// If there are partial block, just stored into buffer.
 		if msg.len > 0 {
@@ -113,14 +113,14 @@ fn (mut d Digest) squeeze(mut dst []u8) int {
 	}
 	// The squeezing phase begins after msg is absorbed with an
 	// permutation 𝐴𝑠𝑐𝑜𝑛-𝑝[12] to the state:
-	ascon_pnr(mut d.State, 12)
+	ascon_pnr(mut d.State, ascon_prnd_12)
 
 	mut pos := 0
 	mut clen := dst.len
 	// process for full block size
 	for clen >= block_size {
 		binary.little_endian_put_u64(mut dst[pos..pos + 8], d.State.e0)
-		ascon_pnr(mut d.State, 12)
+		ascon_pnr(mut d.State, ascon_prnd_12)
 		pos += block_size
 		clen -= block_size
 	}
diff --git a/vlib/x/crypto/ascon/util.v b/vlib/x/crypto/ascon/util.v
@@ -8,12 +8,6 @@ module ascon
 import math.bits
 import encoding.binary
 
-// rotate_right_64 rotates x right by k bits
-fn rotate_right_64(x u64, k int) u64 {
-	// call rotate_left_64(x, -k).
-	return bits.rotate_left_64(x, -k)
-}
-
 // clear_bytes clears the bytes of x in n byte
 @[inline]
 fn clear_bytes(x u64, n int) u64 {
@@ -100,8 +94,3 @@ fn store_bytes(mut out []u8, x u64, n int) {
 		out[i] = get_byte(x, i)
 	}
 }
-
-@[inline]
-fn ascon_rotate_right(x u64, n int) u64 {
-	return (x >> n) | x << (64 - n)
-}
diff --git a/vlib/x/crypto/ascon/xof.v b/vlib/x/crypto/ascon/xof.v
@@ -305,15 +305,15 @@ pub fn (mut x CXof128) free() {
 fn cxof128_absorb_custom_string(mut s State, cs []u8) {
 	// absorb Z0, the length of the customization string (in bits) encoded as a u64
 	s.e0 ^= u64(cs.len) << 3
-	ascon_pnr(mut s, 12)
+	ascon_pnr(mut s, ascon_prnd_12)
 
 	// absorb the customization string
 	mut zlen := cs.len
 	mut zidx := 0
 	for zlen >= block_size {
 		block := unsafe { cs[zidx..zidx + block_size] }
 		s.e0 ^= binary.little_endian_u64(block)
-		ascon_pnr(mut s, 12)
+		ascon_pnr(mut s, ascon_prnd_12)
 
 		// updates a index
 		zlen -= block_size
@@ -323,5 +323,5 @@ fn cxof128_absorb_custom_string(mut s State, cs []u8) {
 	last_block := unsafe { cs[zidx..] }
 	s.e0 ^= load_bytes(last_block, last_block.len)
 	s.e0 ^= pad(last_block.len)
-	ascon_pnr(mut s, 12)
+	ascon_pnr(mut s, ascon_prnd_12)
 }
