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Move the Update function before Init #88

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Feb 17, 2025
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Move the Update function before Init #88

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fd57361
Move the Update function before Init
jedisct1 Feb 17, 2025
5048d0b
Remove empty line
jedisct1 Feb 17, 2025
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262 changes: 131 additions & 131 deletions draft-irtf-cfrg-aegis-aead.md
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Original file line number Diff line number Diff line change
Expand Up @@ -356,8 +356,8 @@ Primitives:

AEGIS internal functions:

- `Init(key, nonce)`: the initialization function.
- `Update(M0, M1)` or `Update(M)`: the state update function.
- `Init(key, nonce)`: the initialization function.
- `Absorb(ai)`: the input block absorption function.
- `Enc(xi)`: the input block encryption function.
- `Dec(ci)`: the input block decryption function.
Expand Down Expand Up @@ -501,38 +501,6 @@ else:
return msg
~~~

## The Init Function

~~~
Init(key, nonce)
~~~

The `Init` function constructs the initial state `{S0, ...S7}` using the given `key` and `nonce`.

Inputs:

- `key`: the encryption key.
- `nonce`: the public nonce.

Defines:

- `{S0, ...S7}`: the initial state.

Steps:

~~~
S0 = key ^ nonce
S1 = C1
S2 = C0
S3 = C1
S4 = key ^ nonce
S5 = key ^ C0
S6 = key ^ C1
S7 = key ^ C0

Repeat(10, Update(nonce, key))
~~~

## The Update Function

~~~
Expand Down Expand Up @@ -573,6 +541,38 @@ S6 = S'6
S7 = S'7
~~~

## The Init Function

~~~
Init(key, nonce)
~~~

The `Init` function constructs the initial state `{S0, ...S7}` using the given `key` and `nonce`.

Inputs:

- `key`: the encryption key.
- `nonce`: the public nonce.

Defines:

- `{S0, ...S7}`: the initial state.

Steps:

~~~
S0 = key ^ nonce
S1 = C1
S2 = C0
S3 = C1
S4 = key ^ nonce
S5 = key ^ C0
S6 = key ^ C1
S7 = key ^ C0

Repeat(10, Update(nonce, key))
~~~

## The Absorb Function

~~~
Expand Down Expand Up @@ -838,6 +838,41 @@ else:
return msg
~~~

## The Update Function

~~~
Update(M)
~~~

The `Update` function is the core of the AEGIS-256 algorithm.
It updates the state `{S0, ...S5}` using a 128-bit value.

Inputs:

- `msg`: the 128-bit block to be absorbed.

Modifies:

- `{S0, ...S5}`: the state.

Steps:

~~~
S'0 = AESRound(S5, S0 ^ M)
S'1 = AESRound(S0, S1)
S'2 = AESRound(S1, S2)
S'3 = AESRound(S2, S3)
S'4 = AESRound(S3, S4)
S'5 = AESRound(S4, S5)

S0 = S'0
S1 = S'1
S2 = S'2
S3 = S'3
S4 = S'4
S5 = S'5
~~~

## The Init Function

~~~
Expand Down Expand Up @@ -876,41 +911,6 @@ Repeat(4,
)
~~~

## The Update Function

~~~
Update(M)
~~~

The `Update` function is the core of the AEGIS-256 algorithm.
It updates the state `{S0, ...S5}` using a 128-bit value.

Inputs:

- `msg`: the 128-bit block to be absorbed.

Modifies:

- `{S0, ...S5}`: the state.

Steps:

~~~
S'0 = AESRound(S5, S0 ^ M)
S'1 = AESRound(S0, S1)
S'2 = AESRound(S1, S2)
S'3 = AESRound(S2, S3)
S'4 = AESRound(S3, S4)
S'5 = AESRound(S4, S5)

S0 = S'0
S1 = S'1
S2 = S'2
S3 = S'3
S4 = S'4
S5 = S'5
~~~

## The Absorb Function

~~~
Expand Down Expand Up @@ -1139,6 +1139,40 @@ else:

## AEGIS-128X

### The Update Function

~~~
Update(M0, M1)
~~~

The AEGIS-128X `Update` function is similar to the AEGIS-128L `Update` function but absorbs `R` (= `256 * D`) bits at once. `M0` and `M1` are `128 * D` bits instead of 128 bits but are split into 128-bit blocks, each of them updating a different AEGIS-128L state.

Steps:

~~~
m0 = Split(M0, 128)
m1 = Split(M1, 128)

for i in 0..D:
V'[0,i] = AESRound(V[7,i], V[0,i] ^ m0[i])
V'[1,i] = AESRound(V[0,i], V[1,i])
V'[2,i] = AESRound(V[1,i], V[2,i])
V'[3,i] = AESRound(V[2,i], V[3,i])
V'[4,i] = AESRound(V[3,i], V[4,i] ^ m1[i])
V'[5,i] = AESRound(V[4,i], V[5,i])
V'[6,i] = AESRound(V[5,i], V[6,i])
V'[7,i] = AESRound(V[6,i], V[7,i])

V[0,i] = V'[0,i]
V[1,i] = V'[1,i]
V[2,i] = V'[2,i]
V[3,i] = V'[3,i]
V[4,i] = V'[4,i]
V[5,i] = V'[5,i]
V[6,i] = V'[6,i]
V[7,i] = V'[7,i]
~~~

### The Init Function

~~~
Expand Down Expand Up @@ -1178,40 +1212,6 @@ Repeat(10,
)
~~~

### The Update Function

~~~
Update(M0, M1)
~~~

The AEGIS-128X `Update` function is similar to the AEGIS-128L `Update` function but absorbs `R` (= `256 * D`) bits at once. `M0` and `M1` are `128 * D` bits instead of 128 bits but are split into 128-bit blocks, each of them updating a different AEGIS-128L state.

Steps:

~~~
m0 = Split(M0, 128)
m1 = Split(M1, 128)

for i in 0..D:
V'[0,i] = AESRound(V[7,i], V[0,i] ^ m0[i])
V'[1,i] = AESRound(V[0,i], V[1,i])
V'[2,i] = AESRound(V[1,i], V[2,i])
V'[3,i] = AESRound(V[2,i], V[3,i])
V'[4,i] = AESRound(V[3,i], V[4,i] ^ m1[i])
V'[5,i] = AESRound(V[4,i], V[5,i])
V'[6,i] = AESRound(V[5,i], V[6,i])
V'[7,i] = AESRound(V[6,i], V[7,i])

V[0,i] = V'[0,i]
V[1,i] = V'[1,i]
V[2,i] = V'[2,i]
V[3,i] = V'[3,i]
V[4,i] = V'[4,i]
V[5,i] = V'[5,i]
V[6,i] = V'[6,i]
V[7,i] = V'[7,i]
~~~

### The Absorb Function

~~~
Expand Down Expand Up @@ -1347,6 +1347,35 @@ return tag

## AEGIS-256X

### The Update Function

~~~
Update(M)
~~~

The AEGIS-256X `Update` function is similar to the AEGIS-256 `Update` function but absorbs `R` (`128 * D`) bits at once. `M` is `128 * D` bits instead of 128 bits and is split into 128-bit blocks, each of them updating a different AEGIS-256 state.

Steps:

~~~
m = Split(M, 128)

for i in 0..D:
V'[0,i] = AESRound(V[5,i], V[0,i] ^ m[i])
V'[1,i] = AESRound(V[0,i], V[1,i])
V'[2,i] = AESRound(V[1,i], V[2,i])
V'[3,i] = AESRound(V[2,i], V[3,i])
V'[4,i] = AESRound(V[3,i], V[4,i])
V'[5,i] = AESRound(V[4,i], V[5,i])

V[0,i] = V'[0,i]
V[1,i] = V'[1,i]
V[2,i] = V'[2,i]
V[3,i] = V'[3,i]
V[4,i] = V'[4,i]
V[5,i] = V'[5,i]
~~~

### The Init Function

~~~
Expand Down Expand Up @@ -1404,35 +1433,6 @@ Repeat(4,
)
~~~

### The Update Function

~~~
Update(M)
~~~

The AEGIS-256X `Update` function is similar to the AEGIS-256 `Update` function but absorbs `R` (`128 * D`) bits at once. `M` is `128 * D` bits instead of 128 bits and is split into 128-bit blocks, each of them updating a different AEGIS-256 state.

Steps:

~~~
m = Split(M, 128)

for i in 0..D:
V'[0,i] = AESRound(V[5,i], V[0,i] ^ m[i])
V'[1,i] = AESRound(V[0,i], V[1,i])
V'[2,i] = AESRound(V[1,i], V[2,i])
V'[3,i] = AESRound(V[2,i], V[3,i])
V'[4,i] = AESRound(V[3,i], V[4,i])
V'[5,i] = AESRound(V[4,i], V[5,i])

V[0,i] = V'[0,i]
V[1,i] = V'[1,i]
V[2,i] = V'[2,i]
V[3,i] = V'[3,i]
V[4,i] = V'[4,i]
V[5,i] = V'[5,i]
~~~

### The Absorb Function

~~~
Expand Down