Skip to content

Bring profiles into the modern day #307

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
aarongable wants to merge 9 commits into
base: main
Choose a base branch
from
Open

Bring profiles into the modern day #307

Changes from all commits
Commits
Show all changes
9 commits
Select commit Hold shift + click to select a range
5b097a0
Bring profiles into the modern day
aarongable Oct 15, 2025
9d053b7
Review comments
aarongable Nov 7, 2025
2d991a4
Rebase fixes
aarongable Jul 7, 2026
6adcd83
Edits for clarity
aarongable Jul 9, 2026
1a34247
Express all validities in days
aarongable Jul 22, 2026
7e6d2e0
Change how we talk about serial numbers
aarongable Jul 23, 2026
39c1e04
Give ourselves a buffer in both directions for serial length
aarongable Jul 24, 2026
bf4cdd8
Make keyEncipherment optional even for RSA keys
aarongable Jul 24, 2026
90933e2
Clarify that cross-sign keys must match original keys
aarongable Jul 30, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
156 changes: 101 additions & 55 deletions CP-CPS.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -987,70 +987,116 @@ See [Section 5.5.5](#555-requirements-for-time-stamping-of-records).

## 7.1 Certificate profile

All ISRG Certificates adhere to one of the following Certificate Profiles, which are derived from the profiles with the same names found in Section 7.1.2 of the Baseline Requirements. Fields and extensions not specifically mentioned are as specified in RFC 5280 and the Baseline Requirements.
All ISRG Certificates are issued in accordance with one of the following Certificate Profiles, which are derived from the profiles with the same names found in Section 7.1.2 of the Baseline Requirements.

### Root CA Certificate Profile

| Field or extension | Value |
| ------------------------------ | ------------------------------------------------------------------------|
| Serial Number | Unique, with 64 bits of output from a CSPRNG |
| Issuer Distinguished Name | C=US, O=Internet Security Research Group or O=ISRG, and a meaningful CN |
| Subject Distinguished Name | Same as Issuer DN |
| Validity Period | Up to 25 years |
| Basic Constraints | cA=True, pathLength constraint absent (critical) |
| Subject Public Key | See Sections 6.1.5, 6.1.6, and 7.1.3.1 |
| Key Usage | keyCertSign, cRLSign (critical) |
| **Field** | **Description** |
| ---- | ------ |
| `tbsCertificate` | |
|     `version` | See [Section 7.1.1](#711-version-numbers) |
|     `serialNumber` | More than 100 bits of output from a CSPRNG, optionally with additional non-random bits |
|     `signature` | See [Section 7.1.3.2](#7132-signature-algorithmidentifier) |
|     `issuer` | Byte-for-byte identical to the `subject` field |
|     `validity` | At most 3660 days (approx. 10 years) |
|     `subject` | C=US, O=ISRG, and a unique CN |
|     `subjectPublicKeyInfo` | See Sections [6.1.5](#615-key-sizes), [6.1.6](#616-public-key-parameters-generation-and-quality-checking), and [7.1.3.1](#7131-subjectpublickeyinfo) |
|     `issuerUniqueID` | Not present |
|     `subjectUniqueID` | Not present |
|     `extensions` | |
|         `basicConstraints` | Critical, with `cA` set to true |
|         `keyUsage` | Critical, with only the `keyCertSign` (5) and `cRLSign` (6) bits set |
|         `subjectKeyIdentifier` | Contains a truncated hash of the `subjectPublicKey`, per Section 2(1) of RFC 7093 |
|         Any other extension | Not present |
| `signatureAlgorithm` | Byte-for-byte identical to the `tbsCertificate.signature` |
| `signatureValue` | A signature appropriate to the `signatureAlgorithm` field |

### Cross-Certified Subordinate CA Certificate Profile

| Field or extension | Value |
| ------------------------------ | ----------------------------------------------------------------------------- |
| Serial Number | Unique, with 64 bits of output from a CSPRNG |
| Issuer Distinguished Name | Derived from Issuer certificate |
| Subject Distinguished Name | Identical to the existing CA certificate |
| Validity Period | Up to 8 years |
| Basic Constraints | Identical to the existing CA certificate |
| Key Usage | Identical to the existing CA certificate |
| Extended Key Usage | TLS Server Authentication and optionally TLS Client Authentication |
| Certificate Policies | CAB Forum Domain Validated (2.23.140.1.2.1) |
| Authority Information Access | Contains CA Issuers URL and optionally an OCSP URL; URLs vary based on Issuer |
| Subject Public Key | Identical to the existing CA certificate |
| CRL Distribution Points | Contains a CRL URL; URL varies based on Issuer |
| **Field** | **Description** |
| ---- | ------ |
| `tbsCertificate` | |
|     `version` | See [Section 7.1.1](#711-version-numbers) |
|     `serialNumber` | More than 100 bits of output from a CSPRNG, optionally with additional non-random bits |
|     `signature` | See [Section 7.1.3.2](#7132-signature-algorithmidentifier) |
|     `issuer` | Byte-for-byte identical to the `subject` field of the Issuing CA |
|     `validity` | At most 1098 days (approx. 3 years) |
|     `subject` | Byte-for-byte identical to the `subject` field of the existing CA Certificate |
|     `subjectPublicKeyInfo` | Byte-for-byte identical to the `subjectPublicKeyInfo` field of the existing CA Certificate. See also Sections [6.1.5](#615-key-sizes), [6.1.6](#616-public-key-parameters-generation-and-quality-checking), and [7.1.3.1](#7131-subjectpublickeyinfo) |
|     `issuerUniqueID` | Not present |
|     `subjectUniqueID` | Not present |
|     `extensions` | |
|         `authorityInformationAccess` | Contains the HTTP URI of the Issuing CA's Certificate |
|         `authorityKeyIdentifier` | Contains a `keyIdentifier` byte-for-byte identical to the `subjectKeyIdentifier` of the Issuing CA |
|         `basicConstraints` | Critical, with `cA` set to true and `pathLenConstraint` identical to the existing CA Certificate |
|         `certificatePolicies` | Contains only the Baseline Requirements Domain Validated Reserved Policy Identifier (OID 2.23.140.1.2.1) |
|         `crlDistributionPoints` | Contains the HTTP URI of a CRL issued by the Issuing CA whose scope includes this certificate |
|         `extKeyUsage` | Contains only `id-kp-serverAuth` (OID 1.3.6.1.5.5.7.3.1) |
|         `keyUsage` | Critical, with only the `keyCertSign` (5) and `cRLSign` (6) bits set |
|         `subjectKeyIdentifier` | Byte-for-byte identical to the `subjectKeyIdentifier` of the existing CA Certificate |
|         Any other extension | Not present |
| `signatureAlgorithm` | Byte-for-byte identical to the `tbsCertificate.signature` |
| `signatureValue` | A signature appropriate to the `signatureAlgorithm` field |

### TLS Subordinate CA Certificate Profile

| Field or extension | Value |
| ------------------------------ | ----------------------------------------------------------------------------- |
| Serial Number | Unique, with 64 bits of output from a CSPRNG |
| Issuer Distinguished Name | Derived from Issuer certificate |
| Subject Distinguished Name | C=US, O=Let's Encrypt, and a meaningful CN |
| Validity Period | Up to 8 years |
| Basic Constraints | cA=True, pathLength constraint 0 (critical) |
| Key Usage | keyCertSign, cRLSign, digitalSignature (critical) |
| Extended Key Usage | TLS Server Authentication and optionally TLS Client Authentication |
| Certificate Policies | CAB Forum Domain Validated (2.23.140.1.2.1) |
| Authority Information Access | Contains CA Issuers URL and optionally an OCSP URL; URLs vary based on Issuer |
| Subject Public Key | See Sections 6.1.5, 6.1.6, and 7.1.3.1 |
| CRL Distribution Points | Contains a CRL URL; URL varies based on Issuer |

### Subscriber (End-Entity) Certificate and Precertificate Profile

| Field or extension | Value |
| --------------------------------- | --------------------------------------------------------------------------------- |
| Serial Number | Unique, with 64 bits of output from a CSPRNG |
| Issuer Distinguished Name | Derived from Issuer certificate |
| Subject Distinguished Name | CN=none, or one of the values from the Subject Alternative Name extension |
| Validity Period | Up to 100 days |
| Basic Constraints | cA=False (critical) |
| Key Usage | digitalSignature, and optionally keyEncipherment (critical) |
| Extended Key Usage | TLS Server Authentication and optionally TLS Client Authentication |
| Certificate Policies | CAB Forum Domain Validated (2.23.140.1.2.1) |
| Authority Information Access | Contains CA Issuers URL and optionally an OCSP URL; URLs vary based on Issuer |
| Subject Public Key | See Sections 6.1.5, 6.1.6, and 7.1.3.1 |
| Subject Alternative Name | A sequence of 1 to 100 dNSNames or ipAddresses (critical if no CN) |
| Precertificate poison | Per RFC 6962 (precertificates only, critical) |
| Signed Certificate Timestamp List | Per RFC 6962 (final certificates only) |
| CRL Distribution Point | If present, contains a URI to the CRL shard whose scope includes this certificate |
| **Field** | **Description** |
| ---- | ------ |
| `tbsCertificate` | |
|     `version` | See [Section 7.1.1](#711-version-numbers) |
|     `serialNumber` | More than 100 bits of output from a CSPRNG, optionally with additional non-random bits |
|     `signature` | See [Section 7.1.3.2](#7132-signature-algorithmidentifier) |
|     `issuer` | Byte-for-byte identical to the `subject` field of the Issuing CA |
|     `validity` | At most 1098 days (approx. 3 years) |
|     `subject` | C=US, O=Let's Encrypt, and a unique CN |
|     `subjectPublicKeyInfo` | See Sections [6.1.5](#615-key-sizes), [6.1.6](#616-public-key-parameters-generation-and-quality-checking), and [7.1.3.1](#7131-subjectpublickeyinfo) |
|     `issuerUniqueID` | Not present |
|     `subjectUniqueID` | Not present |
|     `extensions` | |
|         `authorityInformationAccess` | Contains the HTTP URI of the Issuing CA's Certificate |
|         `authorityKeyIdentifier` | Contains a `keyIdentifier` byte-for-byte identical to the `subjectKeyIdentifier` of the Issuing CA |
|         `basicConstraints` | Critical, with `cA` set to true and `pathLenConstraint` set to 0 |
|         `certificatePolicies` | Contains only the Baseline Requirements Domain Validated Reserved Policy Identifier (OID 2.23.140.1.2.1) |
|         `crlDistributionPoints` | Contains the HTTP URI of a CRL issued by the Issuing CA whose scope includes this certificate |
|         `extKeyUsage` | Contains only `id-kp-serverAuth` (OID 1.3.6.1.5.5.7.3.1) |
|         `keyUsage` | Critical, with only the `digitalSignature` (0), `keyCertSign` (5), and `cRLSign` (6) bits set |
|         `subjectKeyIdentifier` | Contains a truncated hash of the `subjectPublicKey`, per Section 2(1) of RFC 7093 |
|         Any other extension | Not present |
| `signatureAlgorithm` | Byte-for-byte identical to the `tbsCertificate.signature` |
| `signatureValue` | A signature appropriate to the `signatureAlgorithm` field |

### Subscriber (Server) Certificate Profile

| **Field** | **Description** |
| ---- | ------ |
| `tbsCertificate` | |
|     `version` | See [Section 7.1.1](#711-version-numbers) |
|     `serialNumber` | More than 100 bits of output from a CSPRNG, optionally with additional non-random bits |
|     `signature` | See [Section 7.1.3.2](#7132-signature-algorithmidentifier) |
|     `issuer` | Byte-for-byte identical to the `subject` field of the Issuing CA |
|     `validity` | At most 100 days |
|     `subject` | CN omitted, or optionally contains one of the values from the Subject Alternative Name extension |
|     `subjectPublicKeyInfo` | See Sections [6.1.5](#615-key-sizes), [6.1.6](#616-public-key-parameters-generation-and-quality-checking), and [7.1.3.1](#7131-subjectpublickeyinfo) |
|     `issuerUniqueID` | Not present |
|     `subjectUniqueID` | Not present |
|     `extensions` | |
|         `authorityInformationAccess` | Contains the HTTP URI of the Issuing CA's Certificate |
|         `authorityKeyIdentifier` | Contains a `keyIdentifier` byte-for-byte identical to the `subjectKeyIdentifier` of the Issuing CA |
|         `basicConstraints` | Critical, with `cA` set to false |
|         `certificatePolicies` | Contains only the Baseline Requirements Domain Validated Reserved Policy Identifier (OID 2.23.140.1.2.1) |
|         `crlDistributionPoints` | Contains the HTTP URI of a CRL issued by the Issuing CA whose scope includes this certificate |
|         `extKeyUsage` | Contains only `id-kp-serverAuth` (OID 1.3.6.1.5.5.7.3.1) |
|         `keyUsage` | Critical, with only the `digitalSignature` (0) bit (and optionally the `keyEncipherment` (2) bit, for RSA keys) set |
|         `SignedCertificateTimestampList` | Contains at least two SCTs from logs run by different operators |
|         `subjectAltName` | A sequence of 1 to 100 names of type `dNSName` or `ipAddress` (critical if CN omitted) |
|         `subjectKeyIdentifier` | Optionally contains a truncated hash of the `subjectPublicKey`, per Section 2(1) of RFC 7093 |
|         Any other extension | Not present |
| `signatureAlgorithm` | Byte-for-byte identical to the `tbsCertificate.signature` |
| `signatureValue` | A signature appropriate to the `signatureAlgorithm` field |

### Precertificate Profile

Identical to the Subscriber (Server) Certificate Profile, except that the `SignedCertificateTimestampList` extension is omitted, and a critical "CT poison" extension (OID 1.3.6.1.4.1.11129.2.4.3) is included. ISRG Precertificates are issued directly by the Issuing CA, not by a delegated Precertificate Signing CA.

### 7.1.1 Version number(s)

Expand Down
Loading