isign

Isign is a command-line utility used to sign iOS application packages (IPAs) with a user-supplied signing identity and provisioning profile. It is commonly employed to re-sign apps for testing on physical devices, for enterprise or ad-hoc distribution, or within continuous integration workflows where Xcode signing is inconvenient or unavailable. Isign is typically used by developers and teams who need to create distributable IPAs that are not intended for the App Store.

The tool works by taking an IPA, applying a signing identity from the macOS keychain and a provisioning profile, and producing a re-signed IPA that can be installed on devices included in the provisioning profile. Some implementations may also adjust entitlements or re-sign embedded binaries within the IPA to ensure a valid code signature. The result is an IPA that reflects the specified signing credentials and provisioning constraints.

Requirements for using isign generally include a macOS environment, access to the Xcode command-line tools, and a valid signing certificate stored in the keychain along with a provisioning profile compatible with the target devices. The intended use is typically development, testing, or enterprise distribution; it is not a tool for distributing apps through the official App Store.

Limitations and considerations include adherence to Apple’s code-signing rules and provisioning constraints. Re-signing an IPA does not guarantee successful installation on all devices or in all contexts, and users should ensure compliance with licensing and platform terms. Isign exists within the broader ecosystem of iOS code-signing tools and workflows, alongside Apple’s own codesign and provisioning profile mechanisms.

See also: code signing, provisioning profile, IPA, codesign.