def openssl_verify(data, sig, key, md='sha1'):
    from M2Crypto import X509
    x509 = X509.load_cert_string(key)
    pubkey = x509.get_pubkey()
    pubkey.reset_context(md=md)
    pubkey.verify_init()
    pubkey.verify_update(data)
    return pubkey.verify_final(sig)

data = "1900847_4aaa6c7038653ad2e4dbeba175a679ba_1234576800"
signature = "FkUmueUWrGShv3i+QYPJLFQA5XQeIIXJVFaOzr6lMgHUGCF4dd179atPUKG0FM+JVDF/ole+ZflQo44RU7sSa+NMaFh490ZLbCoz2hNx0c0FTjxKCXWvW9mSuRYOHutfUkIUX1/znwOzm2hqTo20qztO+X751ZaOtcQe6idaz94="
public_key = "-----BEGIN PUBLIC KEY-----\nMIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQDfG4IuFO2h/LdDNmonwGNw5srW\nnUEWzoBrPRF1NM8LqpOMD45FAPtZ1NmPtHGo0BAS1UsyJEGXx0NPJ8Gw1z+huLrl\nXnAVX5B4ec6cJfKKmpL/l94WhP2v8F3OGWrnaEX1mLMoxe124Pcfamt0SPCGkeal\nVvXw13PLINE/YptjkQIDAQAB\n-----END PUBLIC KEY-----\n"
decoded_signature = signature.decode('base64')
# prints "-1":
print openssl_verify(data, decoded_signature, public_key);