Re: [Sidrops] Signed Object signed with Ed25519 (RFC 8419 proof-of-concept)

Job Snijders <> Mon, 04 September 2023 16:36 UTC

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Date: Mon, 04 Sep 2023 18:36:15 +0200
From: Job Snijders <>
To: Russ Housley <>
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Subject: Re: [Sidrops] Signed Object signed with Ed25519 (RFC 8419 proof-of-concept)
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On Mon, Sep 04, 2023 at 06:14:05PM +0200, Job Snijders wrote:
> For comparison I generated a secp256r1 variant of the same ASPA object,
> it clocks in as the second smallest:
> RSA EE w/ RSA CA:              1701 bytes [1]
> secp256k1 w/ sha256 w/ RSA CA: 1463 bytes [3]
> secp256r1 w/ sha256 w/ RSA CA: 1284 bytes (attached)
> Ed25519 w/ sha512 w/ RSA CA:   1281 bytes [2]
> The 179 byte difference between secp256k1 and secp256r1 is caused by the
> secp256k1 public key being encoded differently. The secp256k1 public key
> is encoded in 'explicit form', this means that in addition to the 64
> byte public key, also a large prime, A & B fields, an uncompressed
> Generator field, and an Order field are encoded.

Ah, upon further inspection, the secp256k1 parameters explicitly encoded
turned out to be optional. The final results:

EE        MD     CA   size       decrease (compared to RSA)
RSA       sha256 RSA: 1701 bytes 00.0% (note: the current status)
secp256r1 sha256 RSA: 1284 bytes 24.5%
secp256k1 sha256 RSA: 1282 bytes 24.6%
Ed25519   sha512 RSA: 1281 bytes 24.7% (note: SHA-512 instead of 256)

Are there any other signing/hashing algorithms people would suggest I
try to generate a test object with?

Kind regards,