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Clarify concatenation operations #9

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Clarify concatenation operations #9

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e0192aa
Clarify concatenation operations
bluegate010 Mar 7, 2025
ec575c8
Use concat() operation instead of || syntax.
bluegate010 Mar 7, 2025
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12 changes: 6 additions & 6 deletions draft-irtf-cfrg-hybrid-kems.md
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Original file line number Diff line number Diff line change
Expand Up @@ -573,7 +573,7 @@ def Encaps(pk):
ek = P-256.RandomScalar()
trad_CT = P-256.SerializeElement(P-256.ScalarBaseMult(ek))
trad_SS = P-256.SerializeElementAsSharedSecret(P-256.ScalarMult(trad_PK, ek))
ss = SHA3-256(pq_SS, trad_SS, trad_CT, pk[1184:1217], label)
ss = SHA3-256(concat(pq_SS, trad_SS, trad_CT, pk[1184:1217], label))
ct = concat(pq_CT, trad_CT)
return (ss, ct)
~~~
Expand All @@ -600,7 +600,7 @@ def EncapsDerand(pk, randomness):
ek = P-256.ScalarFromBytes(randomness[32:80])
trad_CT = P-256.SerializeElement(P-256.ScalarMultBase(ek))
trad_SS = P-256.SerializeElementAsSharedSecret(P-256.ScalarMult(ek, trad_PK))
ss = SHA3-256(pq_SS, trad_SS, trad_CT, trad_PK, label)
ss = SHA3-256(concat(pq_SS, trad_SS, trad_CT, trad_PK, label))
ct = concat(pq_CT, trad_CT)
return (ss, ct)
~~~
Expand All @@ -619,7 +619,7 @@ def Decaps(sk, ct):
trad_CT = P-256.DeserializeElement(ct[1088:1121])
pq_SS = ML-KEM-768.Decapsulate(pq_SK, pq_CT)
trad_SS = P-256.SerializeElementAsSharedSecret(P-256.ScalarMult(trad_SK, trad_CT))
return SHA3-256(pq_SS, trad_SS, ct[1088:1121], trad_PK, label)
return SHA3-256(concat(pq_SS, trad_SS, ct[1088:1121], trad_PK, label))
~~~

`ct` is the 1121-byte ciphertext resulting from Encaps() and `sk` is a
Expand Down Expand Up @@ -910,7 +910,7 @@ def Encaps(pk):
ek = P-384.RandomScalar()
trad_CT = P-384.SerializeElement(P-384.ScalarBaseMult(ek))
trad_SS = P-384.SerializeElementAsSharedSecret(P-384.ScalarMult(trad_PK, ek))
ss = SHA3-256(pq_SS, trad_SS, trad_CT, pk[1568:1629], label)
ss = SHA3-256(concat(pq_SS, trad_SS, trad_CT, pk[1568:1629], label))
ct = concat(pq_CT, trad_CT)
return (ss, ct)
~~~
Expand All @@ -937,7 +937,7 @@ def EncapsDerand(pk, randomness):
ek = P-384.ScalarFromBytes(randomness[32:80])
trad_CT = P-384.SerializeElement(P-384.ScalarMultBase(ek))
trad_SS = P-384.SerializeElementAsSharedSecret(P-384.ScalarMult(ek, trad_PK))
ss = SHA3-256(pq_SS, trad_SS, trad_CT, pk[1568:1629], label)
ss = SHA3-256(concat(pq_SS, trad_SS, trad_CT, pk[1568:1629], label))
ct = concat(pq_CT, trad_CT)
return (ss, ct)
~~~
Expand All @@ -956,7 +956,7 @@ def Decaps(sk, ct):
trad_CT = P-384.DeserializeElement(ct[1568:1629])
pq_SS = ML-KEM-1024.Decapsulate(pq_SK, pq_CT)
trad_SS = P-384.SerializeElementAsSharedSecret(P-384.ScalarMult(trad_SK, trad_CT))
return SHA3-256(pq_SS, trad_SS, ct[1568:1629], trad_PK, label)
return SHA3-256(concat(pq_SS, trad_SS, ct[1568:1629], trad_PK, label))
~~~

`ct` is the 1629-byte ciphertext resulting from Encaps() and `sk` is a
Expand Down